They're plastic, actually, but the other ones you mention are worse.

> we have things like infusions (ginger, mint, fruits, but also Rooibos) that doesn't really "do" anything but definitely make for a tasty hydrating drink.

Rooibos, for certain, 'does' a lot. It lowers your blood pressure. You can use it as a downer though it might be unnecessary if you don't use caffeine otherwise.