Can You Put Soda in a Thermos?

Can you put soda in a thermos or will it actually damage your thermos, make your soda taste bad or potentially even leech metals into your drink?

If you can put soda in a thermos will it keep it fizzy or will the soda lose all of its carbonation?

Send Mrs a great at keeping drinks cold all day long and are primarily designed for either water or hot food. But if you're drinking soda instead of water you might want to know whether or not you can put soda in your thermos and if it's safe.

I'm personally a fan of energy drinks and while I'm trying to stop drinking them I wanted to know if I could use my thermos to keep them cold all day long.

It's completely fine to put soda in a Thermos bottle, cup or flask. The airtight Thermos will keep your soda fizzy and the vacuum insulation will keep it cold.

Research shows soda should NOT affect stainless steel but some people claim their Thermos imparts a metallic taste into their soda.

I couldn't find an answer from Thermos themselves so I did a fair amount of research into what can happen with soda and stainless steel as well as what things other brands are saying about soda in their vacuum insulated cups and bottles.

See the latest price of Thermos tumblers and flasks at Amazon

What Are The Risks of Putting Soda in a Thermos?

Why are people worried about drinking soda out of the thermos? What could potentially cause any issues and is there actually anything to be worried about here?

Well it turns out there's actually a few reasonable concerns people have about putting soda in their thermos:

Carbonation and Expansion Breaking Your Bottle

Soda contains dissolved carbon dioxide which is what creates its fizziness.

When placed in a bottle the carbon dioxide wants to expand into gas and this creates pressure inside the can or bottle.

SSo you can understand that people get concerned that this pressure could be too much for the thermostat handle and it may actually break the furnace or ruin the insulation. However this isn't the case.

Thermoses and other vacuum insulated cups and bottles can easily handle the pressure created by soda or sparkling water. You may get some pressure release when you open your thermos but it's not going to cause any damage.

However, you do need to be aware of this as it could potential he cause your thermos lid to get stuck and be difficult to open.

This is only really likely to cause you issues if you leave the soda in your thermos for a very long time and it starts to ferment and go off. As the bacteria grows the release gases building up more pressure and putting pressure on the lid making it hard to open. If your lid does get stuck here at 12 ways to get a lid unstuck.

Also it's a good idea to be careful when unscrewing the lid of your thermos when you have soda in your cup or bottle. Below is a funny story of someone who opened up their Hydro Flask bottle when it had soda in it.

Check out the story below from this Facebook post:

When I had sparkling water in mine, the lid popped off a good 15 feet when I turned it to open it and the inner ring also popped out of it.

A lot of thermoses now come with lids that can be partially opened allowing you to release pressure without having your lid fly off.

Acidity Corroding The Stainless Steel

Did you know that soda is actually quite acidic? Most people don't realize this because soda is so sweet.

Soda usually has a PH level ranging for 2.38-3.70. This means they can be as much as 100,000 times more acidic than water. That's pretty acidic.

So soda can actually be corrosive so some people worry that it may actually corrode the stainless steel in the thermos and cause the stainless steel to leech chemicals into their drink.

There's no clear evidence that this happens and wikipedia states that stainless steel resists corrosions of most acids including the phosphoric acid found in coca-cola:

All types of stainless steel resist attack from phosphoric acid and nitric acid at room temperature.

I looked at this in more detail in my article on do Hydro Flask bottles rust?

Build Up of Residue

Leaving soda inside your thermos can build up a sticky residue on the inside walls of your thermos that can be difficult to clean off. You might need to scrub really hard with an abrasive cleaner to get it off.

Are used to work in a café and we would soak our stainless steel milk jugs in Coca-Cola overnight to help remove milk stains and buildup. But cleaning off the Coca-Cola residue would take a lot of effort and scrubbing and this can be hard to do in a thermos where you can't fit your hand inside.

Leaving soda in your Yeti can cause a build up of residue on the inside walls of your Yeti. This can be really hard to clean off without scrubbing it really good with an abrasive cleaner.

What Does Thermos Say About Soda In Their Bottles?

You might want to know what thermos says about putting soda in their products. However, I searched their FAQ page and couldn't find any details relating to soda.

I did find this Amazon Question where someone asked if you can put soda in a vacuum insulated stainless steel bottle similar to Thermos and the answers were that yes this would be completely fine and shouldn't cause any issues.

See the latest price of Thermos tumblers and flasks at Amazon

What Do Other Companies Say About Soda In Their Bottles

There are a variety of different brands of vacuum insulated stainless steel bottles which are very similar to thermos.

So I wanted to look at what they said and see whether or not they thought it was OK to put soda in their bottles.

Yeti clearly state on their Yeti Rambler FAQ page:

The tumblers will keep your soda, beer, wine, smoothie, or mixed drinks ice cold.

Cambak said on this FAQ page:

Just about anything (milk, juice, sports drinks) works as long as you clean your bottle after each use. We don’t recommend putting carbonated beverages in the eddy, since the pressure can cause liquid to spurt out of the straw. However, it’s fine to put carbonated drinks in the Chute or Podium series bottles.

What Do Regular People Say About Soda in their Thermos?

I can imagine there would be lots of people out there using their thermos to keep their soda called on a day-to-day basis. So I search the web to see what other people were saying about using their thermoses for soda.

There was this answer on Quora when someone asked about putting soda in a Thermos:

Yes, you can fill your thermos with soda. You can pretty much fill it with any beverage – even soup (not sure if soup is considered a beverage.)

This reddit thread had a lot of concerns about pressure build up in thermoses, particularly glass lined thermoses.

One reason is some thermos bottles use glass containers inside which will shatter with the pressure built up by the increased pressure when the liquid is agitated and the gas is released.

However, the general consensus is that there shouldn't be any issues when putting soda in your thermos.

When I was looking into if you can put lemon juice in a Hydro Flask a lot of people out there claimed that lemon juice caused a metallic taste in their Hydro Flask.

However, I did not find this when looking into soda.

I am yet to see one complaint about metallic tasting soda in a Thermos or any other stainless steel tumbler or bottle. I am unsure if this is due to lemon reacting more with stainless steel or to people just not being able to taste it through the sweetness of the soda.

Soda Is Made In Stainless Steel Tanks

More often than not people buy soda in plastic bottles or in alluminum cans (which actually have a thin plastic layer inside it). So you may not realize that all major sodas actually made in large stainless steel that before they packaged into the plastic bottles and put on the shelves.

Well the stainless steel using these fats is a slightly different grade than that inside your thermos it's extremely similar in its make up.

So before you ever put your soda inside a thermos it's spent a lot of its life inside stainless steel already.

If soda and stainless steel didn't go well together then I imagine they wouldn't be using so much stainless steel in the factories that actually make the soda.

Will Soda Stay Fizzy In a Thermos?

Soda contains dissolved carbon dioxide which wants to escape and when exposed to the outside air soda will lose its fizz because the carbon dioxide will escape into the air.

It's also interesting that soda stays fizzy longer when it is colder. As it warms up it actually loses more of its fizz.

A Thermos will keep soda fizzy and stop it going flat because it's airtight and keeps the soda cold. For best results fill your Thermos to the top so there is no air space of the carbon dioxide to escape into.

Will The Phosphoric Acid in Coca-Cola Corrode Your Thermos?

Phosphoric acid is great for dissolving and removing rust and Coca-Cola happens to contain phosphoric acid. This actually makes it perfect to help you clean rust from stainless steel bottles.

Thermoses are made from kitchen grade 18/8 stainless steel and are corrosion resistant and thus shouldn't react much to phosphoric acid in Coca-Cola. The acid will dissolve and remove existing rust but it's not like to cause rust to occur.

So it should be fine to keep Coca-Cola in your Thermos.

See the latest price of Thermos tumblers and flasks at Amazon

Can You Put Carbonated Drinks In a Thermos?

What about carbonated drinks other than Soda? Sparkling water or sparkling wine or beer or champagne?

Can you put other carbonated drinks in a Thermos?

It's fine to put all forms of carbonated drinks in a stainless steel thermos. It can easily handle the pressure from carbonation and is corrosion resistant. However, don't put carbonated beverages in a glass lined thermos as they can break.

Thermoses will keep your carbonated drinks cold and given that they are airtight they will stop them from going flat as well.

Can You Put Sparkling Water In A Yeti Cup or Bottle?

My girlfriend loves sparkling water and she prefers to drink it over regular water. But can you put sparkling water in a thermos?

You can put sparkling water in a thermos without any issues. The stainless steel walls of the thermos can handle the pressure from carbonation and the water is an acidic so won't corrode the Thermos.

However you do need to be careful putting sparkling water in a glass lined thermos as the pressure from the sparkling water could actually break the glass. This is unlikely but it is possible so you just want to be careful..

Thermoses are airtight when the lid is closed so it'll trap the carbon dioxide and keep your sparkling water as sparkling as possible. For best results fill your thermos to the top so there is no air space for the carbon dioxide to escape into.