grape juice
soda
orange sherbet
lime sherbet

1. Use grape juice and a variety of carbonated soft drinks (club soda, ginger ale, lemon-lime, etc). Mix them in a punch bowl.

2. Take scoops of the orange and lime sherbet and float them in the punch. Let them melt a little, so that a nasty film spreads all over the top of the punch. (There should still be "bubbles" in it in the form of sherbet scoops.)

Looks horrible, tastes just fine.