You need light shining through the liquid from behind.
Joe
Thats where the light was coming from had a flash behind the bottle
It's not lighting up the whiskey enough. You need a reflector behind the bottle to catch light and be visible through the liquid. Here's an example:
Hit me. The bottle and both glasses have carefully trimmed pieces of Styrofoam standing up right behind them. The Styrofoam was trimmed just past the point of being visible from the front. The whole thing is sitting on top of a honeycomb in an 11 inch strobe reflector with holes cut in the seamless to flash the Styrofoam.
Joe