I tried this in the Kitchen (so there was no other water nearby to interfere):
>EXAMINE BOTTLE
The glass bottle contains:
A quantity of water
>FILL SACK WITH WATER
The water leaks out of the brown sack and evaporates.
>EXAMINE BOTTLE
The glass bottle is empty.
Both the bottle and the sack were closed at the time.
It's probably something in WATER-F, which is one of the action routines I still haven't wrapped my head around yet.