Channeling some Billy Joel tonight while listening to my husband play the keyboard with a "drinking alone" shot.
I used the dim ambient light in the room (a lamp with ordinary tungsten bulbs about 6 feet away and close to the ceiling) to light the scene, and held a 580EXII gelled with two 1/4 CTO gels on the end of a 10" snoot directly overhead on 1/64th power.
The glass is actually full, boringly enough with water. Maybe it will get filled with something else now that the shot is finished.
Canon 5D Mark II
105mm - ISO 400