A thermos (or vacuum flask) is honestly a lifesaver when you want your coffee hot during a long day, or your water ice-cold on a hike. But here’s the thing—if you don’t clean it properly, stains and smells start to build up. Suddenly, your fresh tea tastes like yesterday’s coffee. Not fun.

The good news? Keeping your BingoBottle thermos flask clean inside is actually super simple. Here’s a quick step-by-step guide to help you out.

Steps to clean a tumbler properly

Cleaning a stainless steel tumbler is actually a simple task for which no special tools or knowledge are needed, but you do need to keep in mind certain aspects when it comes to making cleaning easier.

The first and most important for BingoBottles stainless steel thermoses is a basic consideration that as manufacturers we do on the maintenance of our products, and is that we strongly recommend not to put them in the dishwasher, as the material and insulating finishes can be compromised by the temperature and cleaning products used by the dishwasher.

Therefore, from BingoBottles, we will always recommend washing the thermos by hand, but here we explain step by step, how to do it.

You will see that this procedure is very simple:

Step 1: Grab What You’ll Need

• Nothing fancy here—just a few basics:
• A bit of dish soap or mild detergent (nothing too strong)
• Warm water
• A bottle brush (long enough to reach the bottom, soft bristles so you don’t scratch it)
• White vinegar (totally optional, but handy for tough stains)

Step 2: Empty and Rinse

First things first, pour out whatever’s left inside. Give your BingoBottle a good rinse with warm water to get rid of any leftover liquid or residue. Don’t forget the lid and spout—those little spots love to hold onto smells.

Step 3: Mix Your Cleaning Solution

Fill the flask with warm water and just a drop or two of dish soap. Don’t go boiling hot—extreme heat can mess with the insulation.

Got stubborn stains or funky odors? Try mixing equal parts white vinegar and water instead. Vinegar works like magic, but don’t overdo it—you don’t want your drinks smelling like a salad.

Step 4: Scrub the Inside

Dip your brush into the soapy (or vinegar) mix and scrub the inside. Swirl it around the bottom and sides, then give some love to the lid and spout too.

If you’re dealing with extra stubborn stains, let the soapy or vinegar water sit inside for 10–15 minutes before scrubbing. That way it loosens things up.

Step 5: Rinse and Dry

Rinse, rinse, rinse! Seriously, make sure all the soap or vinegar is completely gone—otherwise your coffee will taste… weird.

Once it’s squeaky clean, leave your BingoBottle to air dry with the cap off. Placing it upside down on a dish rack works best so the water can drain out. 
Now that you know how to clean a stainless steel thermos properly, we recommend you visit our collection of tumblers and this selection of the 5 best stainless steel bottles.