Maybe you have heard about the popular and fizzy (and healthy) drink kombucha. Kombucha is a natural food – not a medicine or supplement – it has not been researched at large for any functional benefit, so look at it like a vegetable. It is full of great stuff that our body needs like probiotics and healthy acids. Kombucha is not made with a mushroom (although everyone says so). It is made with 4 ingredients: sugar, tea, water and the scoby. The scoby is the kombucha culture, like what you find in curd or kefir for example, and like these it is classified as a fungus.
It is up to you how much you want to drink in order to feel the healthy benefits. There is no maximum to it. Drink as much as makes you feel good and happy.
By the way, Kombucha is a great cocktail mixer. Try it out!