Don't panic. And please — don't grab steel wool or bleach. Stainless steel is tough, but it's not indestructible. Here's how to actually clean it the right way.

The daily routine (takes 1 minute)
Rinse it right after you finish drinking. Hot water, swish it around, dump it out. That alone prevents 80% of buildup. Once a day, use a soft sponge with a drop of dish soap, warm water, give it a gentle scrub, and rinse well. Never use abrasive pads — they leave tiny scratches where bacteria hide.

When it starts smelling funky
Fill your thermos with hot water and add two tablespoons of white vinegar (or a squeeze of lemon). Let it sit for 30 minutes. Dump, rinse, and the smell is gone. For stronger odours, leave it overnight. Vinegar neutralises without damaging the metal.

For stubborn tea or coffee stains
Baking soda to the rescue. Sprinkle a couple of spoonfuls inside, add a little warm water to make a paste. Scrub gently with a soft sponge, leave it for 10 minutes, then rinse. Or fill with hot water, drop in half a denture tablet, let it fizz for 15 minutes — works like a charm.

Don't forget the lid and seal
This is where everyone slips. The rubber gasket inside the lid traps moisture and grows mould. Pop it out (if it's removable) and wash it separately with soapy water. Use a small brush or a cotton swab to clean the drinking spout and any threads. Rinse thoroughly.

What NOT to do

• No bleach – it can corrode the inner lining.

• No dishwasher – high heat can warp seals and affect vacuum insulation.

• No boiling water – sudden extreme heat can damage the vacuum layer.

• Don't soak the whole thermos in water – water can get trapped between layers and rust the exterior.

Dry it completely
After washing, leave the lid off and turn it upside down on a drying rack. Moisture trapped inside is what causes that musty smell. Air dry for a few hours before closing it up.

How often?
Rinse after every use. Soap wash once a day. Deep clean with vinegar or baking soda once a week if you use it daily. And if the inside starts looking pitted or the vacuum stops working, just get a new one — they don't last forever.

That's it. Clean thermos, clean taste. Your coffee will thank you.