I find if tends to wrk best to apply a tint or texture to the liquid to make it stand out from the glass. Also it helps if the water is 3D and not 2D it looks like the water exists as only a flat plane, that is fine if shooting from above but from the sides it works best if the water has sides :-)

Soften the light too can help. don't use it at 100% but rather use a soft spot light at about 75% and a distand light set to 25% with shadows turned off on the distance light.

This gives a better soft room style lighting like there is day light comming in the window and the rest of teh light is reflected light.