Cleaning a manky thermos flask any ideas?

[FusionChefGeoff]

Tried vinegar and bicarb which was fun but didn't work and now just stinks of vinegar!

It's very old tannin stains from tea - bleach?? Descale tablet?? Any other ideas?

Baking soda (or bicarb) and boiling water

Denture tablet!
I use them for water bottles that can’t go in the dishwasher. Gets them lovely and clean.

Dishwasher tablet and hot water.

Denture tab or milton

Flurgle (great username!) beat me to it, denture tablets are brilliant for cleaning things hard to get to the bottom of to scrub.

DP used to work away and denture tablets saved many a manky thermos from the bin!

I use milton tablets. They also shift tomato stains from plastic

My mum always used one of my dad's denture tablets to clean out the flask.

Denture or Milton/sterilising tablet plus boiling water.

All these recommendations for denture tablets remind me of what my Dad used to do with his dentures - every so often, he soaked the overnight in bleach. He had a lovely smile

put hot water in thermos (don't fill!!) & drop in denture tablet (you can reuse this liquid in any other containers to clean them

Another vote for Milton

Milton here too.

Dishwasher detergent and really hot water should do it. Leave it for a few hours. Cleans deep stains in coffee cups too.

Dishwasher detergent and really hot water should do it. Leave it for a few hours. Cleans deep stains in coffee cups too.

Dishwasher detergent and really hot water should do it. Leave it for a few hours. Cleans deep stains in coffee cups too.

Another vote for Milton