Aqua Pura

 is literally "Pure Water" that is available once the add-on Broken Steel is installed.

Drinking the water after choosing to infect it with the Modified FEV will result in a player debuff (-2 STR and -1 INT) and, if you drink too many, you will die (this is usually any more than two, so be careful.

Bugs

 * Giving any amount of Aqua Pura to Water Beggars will result in their death at the next map change, regardless of whether or not the Aqua Pura contains Modified FEV. (confirmed, PC)