World's Foulest Beverages

I nominate Kombucha. Why?

[K]ombucha may contain some of the following components depending on the source of the culture: Acetic acid, which gives Kombucha that 'kick' to its smell and taste; butyric acid, gluconic acid, glucuronic acid, lactic acid, malic acid, oxalic acid, usnic acid, as well as some B-vitamins.

UPDATE: Timothy Sandefur identifies another promising contender.