Flasks that don't make flasky tea. Do they exist?

[Belleende]

This being the season for being outdoors, but it still being quite parky, I am prone to taking a flask of tea. On a walk, down the allotment etc.

But every flask I have ever owned after a while tastes more of flask than tea. And no one likes a flasky tea. I dont want to buy a new flask every year. Is there a solution I am unaware of? I clean the flask regularly with lemon and bicarb, but it is now 3 years old, and it is getting flaskier by the day

I only put coffee in a flask though I'm usually a tea drinker. Flask tea tastes stewed. Sorry no solution but watching with interest!

Contigo stainless steel thermal cup works for me, and I’m a very fussy tea drinker

The only solution I've come up with is to take a flask of boiling water and teabags or coffee separately and make a fresh cup when you stop for a break. I drink my tea and coffee black though, it might be a bit more faffy if you want milk.