I would set up the cup with juice in a completely darkened room. Place the cup on something that can "catch" the spill. Put the whole set up in front of a white linen bedsheet or white piece of paper. Set one flash up so that is is directd onto the background- make sure there is enough space between the cup and the background. Ste another flash so that it will illuminate the onbect from the front. Put your camera onto a tripod. The flash that is directed onto the background needs to be either seet up in wireless mode (i.e. two Sony flashes) or you need to attach a slave cell to it so that it will be triggered by the onboard flash.
Make sure the camera is set to manual focusing ad the wb to daylight or flash- not AWB. While the light is on- focus on the middle of the cup by placing a spoon in it. Once this is done- turn the light off. Drop an icecube into your cup and then trigger the camera with a remote control. It will be a bit trial and error- so be prepared to do this a couple of times until you get the right moment.
Look at these two threads to see more about how to trigger wireless flashes:http://www.dynaxdigital.com/index.php/topic,9132.0.html http://www.dynaxdigital.com/index.php/topic,7573.0.html
Here some examples of mine- they are by far not perfect:
I am sure others will jump in with some more tips.