Homegrounds is reader-supported. When you buy via the links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Home » How to Clean a Coffee Thermos (4 Ways to Remove Stains and Smell)

How to Clean Your Coffee Thermos (tips to get the smell and stains out)

A coffee thermos keeps your favorite beverage at an optimal temperature throughout the day. It’s portable and durable, but there is one drawback. Namely, due to its specific shape and design, a coffee thermos can be tricky to clean.

Luckily, there are a few tried and tested methods that allow you to keep this coffee container free of stains and unpleasant smell. This article provides a step-by-step guide on how to clean a coffee thermos and ensure the stains and residue don’t interfere with your drink. With the tips you find here, your thermos will be ready for a fresh batch of coffee every morning.

How to clean a thermos

Salt and Ice Method

What You Need

  • Ice, preferably crushed (cubes work as well)
  • 2-3 tbsp of salt (heaping full)

The right amount of salt depends on the size of your thermos. For smaller models, 2 tablespoons should be just enough.


  1. Fill the thermos with crushed ice up to a quarter of the volume. Bagged ice from your local store works great.
  2. Add 2 or 3 tablespoons of salt over the ice. It’s important to do this as fast as possible to avoid melting. Use large-grain salt like sea salt or kosher salt.
  3. Tightly secure the lid and shake the thermos like there’s no tomorrow. The rubbing of ice and salt exfoliates the inside of your thermos without causing any damage. (1)
  4. Empty the thermos when you finish and rinse it thoroughly to remove any residual salt and ice. Then, leave it to dry naturally – with the lid off, of course.

Vinegar and Baking Soda Method

What You Need

  • White vinegar (distilled) – about 4oz (1/2 cup)
  • Baking soda – 1 tbsp (about 0.5oz)
  • Some hot water

The baking soda and white vinegar cocktail froths up. You should make the mixture above the sink to avoid spills.


  1. Pour vinegar and baking soda into your thermos. The trick is to shake the baking soda over the vinegar to allow the chemical reaction to gradually occur.
  2. Wait for the frothing and fizzing to subside, and then fill up the thermos with hot water. It needs to be completely full.
  3. Don’t put the lid back on because the vinegar and baking soda mix is very reactive (2). Leave the substances to dissolve coffee stains for about 10 minutes. Afterward, grab a bottle brush and give the inside of your thermos a thorough cleaning.
  4. Empty the thermos and give it a good rinse. It is best to rinse with hot water to ensure no vinegar or baking soda remains. You can wipe the thermos with a cleaning cloth, but you still need to leave it to dry naturally.

PRO TIP – If the vinegar smell still lingers after rinsing, repeat step 4 until there’s no vinegar smell left.

Dishwasher Powder Method

What You Need

  • 1 tbsp of dishwasher powder – It’s important to use powder (not liquid) for its abrasive properties.
  • Hot water


  1. Put the dishwasher powder into your thermos and pour some hot water over it. This time, you can close the thermos and shake it briefly.
  2. After shaking, fill the thermos to the brim and leave it to soak for a few hours without the lid on. Feel free to leave it in the sink overnight.
  3. Pour out about half the liquid and give the inside a scrub using a bottle brush. Then, empty the thermos and rinse it out a few times. Again, you should let it air-dry.

Denture Tablets Method

What You Need

  • 1-2 denture tablets
  • Lukewarm or hot water

Denture tablets will fizz away these (coffee) deposits and give the tank a bacterial clean-out too.


  1. Pour lukewarm or hot water into the thermos and fill it halfway up. You should leave it to soak for a while before putting in the tablets. It is advisable to swish the thermos a little to make sure the inside is all wet.
  2. Put 1-2 denture tablets and keep the thermos inside the sink because the ingredients cause a chemical reaction. (3)
  3. Let the thermos sit for about half an hour and don’t put the lid back on. Once the thermos has soaked well, scrub the inside with a bottle brush and then empty it.
  4. Rinse the thermos a few times to remove all the denture cleaner leftovers. While drying, your thermos should be right-side up – without the lid, of course.


Now that you know how to clean a coffee thermos, don’t hesitate to give each method a try. It is also important to rinse the thermos as soon as you finish with your coffee. This way, you prevent a build-up of stubborn coffee grime that will be much harder to clean.

But if there’s just too much grime and dirt, perhaps it’s time to get a new coffee thermos. See our list of best coffee thermoses here. You can also check out our number 1 choice for the best travel coffee mugs in this post.


To get the tea stains out of a stainless steel thermos, it is best to use the vinegar and baking soda method. In fact, the mixture can deal with any liquid-based stains inside your coffee thermos.

The foul smell from a stainless steel thermos is best removed with just baking soda and water. A single teaspoon of baking soda is enough. Put the soda in, fill the thermos with water, and let it sit for a while before rinsing.

Your coffee might taste like soap if you haven’t properly rinsed the thermos, especially after using the dishwasher powder method. This indicates that the coffee is not fit for drinking and that you should clean the thermos again.

  1. Rochester A. (2017, July 16). Amazing Scientific Reasons Why Table Salt Is Good for Cleaning & More! Retrieved July 3, 2019, from https://chemistrycachet.com/reasons-why-table-salt-is-good-for-cleaning/
  2. What Happens When You Mix Vinegar and Baking Soda? (n.d.). Retrieved July 3, 2019, from https://www.wonderopolis.org/wonder/what-happens-when-you-mix-vinegar-and-baking-soda
  3. Ketchum, D. (2019, January 10). Ingredients in Denture Cleaners. Retrieved July 3, 2019, from https://healthfully.com/121826-ingredients-denture-cleaners.html
Alex Azoury
Alex is an Editor of Home Grounds, who considers himself as a traveling coffee fanatic. He is passionate about brewing amazing coffee while in obscure locations, and teaching others to do the same.