"You put nasty soup in the bottle! This is Coro's "special" recipe. Set it to [B] on the ["-"] screen and use it. The only way to find out what it tastes like is to drink it."
The Nasty Soup is a soup, and an item in Twilight Princess. It can be found inside of Coro's pot in Faron Woods. Coro will not allow Link to take some of the soup unless he has used his Lantern to start a fire under the pot.
The Nasty Soup will sometimes restore all of Link's hearts, but other times it might take away one of his hearts.