Cleaning your flask can be as easy as one two three. Most, if not all of what you need on how to clean your flask can be found in your home. If you clean your flask regularly, it is a sure way to keep your flask looking and smelling clean and great. It surely can be with you for a long time as long as you keep the habit of cleaning it.

Some flasks are okay to put in the dishwasher while there are many others that are not. Read the labels of your flasks before you clean it so you do not ruin it. Our reviews of our favorite flasks can help you out with those instructions too. You can make your flask last you a lifetime and it all depends on you!

3 Ways on How To Clean A Flask

Clean the inside

If you are putting any liquid other than water in your flask, rinse it out immediately if you can. Whenever alcohol, juice, soda, or any other liquid is sitting in the flask for a long time, chances are the smell will stay in it. In the event that you cannot rinse it as soon as you have downed everything in it, then try not to let it sit there for more than a day.

To clean the inside, you must fill it with warm soapy water. Really good dish soap is recommended so the inside is cleaned thoroughly. For some, this is good enough for a good clean.

But if yours is stained, looks rusty, or needs more cleaning, you should soak it in vinegar and hot water and use a brush to clean it. Here’s a video that goes into more detail about cleaning a coffee-stained thermos flask.

Be mindful that you cannot just use any cleaning product for your flask. Avoid harsh chemicals like bleach or any other strong disinfectants.

Once you have nearly filled your flask, secure the lid and shake it strongly until you feel like all parts of it have been cleaned thoroughly. Open the lid and use a cleaning brush to clean it a bit more. Use a non-abrasive brush that will not ruin your flask.


Now that you have cleaned the inside, it is time to rinse it properly. Try to make it a point not to leave any residue inside. Fill your flask with water and drain several times until the water is clear. You can also shake it while you rinse so all corners of the flask are cleaned out well.

One sure way to get rid of unwanted smells from your flask is to rinse it with a half and half of vinegar and water.

You can have the option to sterilize your flask by pouring hot water inside your flask and leaving it in for a few minutes. Use a funnel and gloves to avoid burning your hands if you use boiling hot water.

Clean the outside

You can polish the outside of your flask. Use the proper polish for what your flask is made out of. Clean it with a fresh cleaning rag or your special polishing cloth and then air dry it with the lid open.

[amazon bestseller=”metal polish” items=”3″]

How Often Should You Clean A Flask

There isn’t a strict number of how many times you should clean your flask. Most people wash and air dry it after every use. It is perfectly good to have two or more thermal flasks so you can always have a clean one. However much you wash and clean your flask is really just up to you. What is important is that you do clean it! Do not let it get to the point where mold has grown in your flask.

It goes without saying that you should clean it on the day you get it. Please do not use your flask when it is brand new. You can simply wash it with lukewarm water and mild soap. You can even do this several times to make sure all the nasties that came with it from when it was made are all gone.


Hopefully, this helps you to clean your flask thoroughly and answer any questions you may have had.