On a small shelf along one of the walls you find a jug with a spigot in its side.

At first you think the jug is an opaque black, with no way to see what is inside.

When an indistinct, pale fleshy....thing squirms along the side of the jug you realize your mistake. 

It's the water that is black. Not the jug itself. 

There's a single clear glass next to the jug, and a now familiar sticky note commanding you to drink.