Bottle of Syrup
From Twinsuniverse
The Bottle of Syrup is a bottle containing 1/2 liter of cherry-flavored syrup, used for either curing purposes, or just for flavour.
Needing to change the water flavour in Principal Island, Twinsen goes to the pharmacy of Citadel Island to take this syrup. He then goes to the Water Tower of Principal Island, and by pouring the syrup into the water tank, he changes the water's flavour. In return to doing so, the librarian lets Twinsen into the Restricted Section of the library, where Twinsen reads about the legend.
Later in the game, Twinsen fills the now empty flask with the Clear Water.