Glycol Punch

Glycol Punch has two primary ingredients:
Diet Mountain Dew, which has an decidedly evil odd yellow glow to it. Diet 
is necessary so that you don't over sugar people. BTW, we also tried other 
sodas, including Squirt, 7-up and Sprite, but none had that evil yellowness.

A flourescent blue liquid. I know for a fact that the raspberry
"little hugs" drinks for kids are the perfect color. There is a recent 
Kool-Aid blue flavor that I'm sure would work well, too.

For the "little hugs" the ratio is about 4-5 barrels to 1 2-liter bottle
of soda. Adjust as you think best. I'd start by pouring out the soda
and adding the blue. You know you've got it right when you get the
sickly yellow-green of many Glycol-based Antifreezes. Plus, when you
drink, it fizzes! 

Source: rec.food.cooking