All you need is plenty of Alka Seltzer and clear soda pop such as 7-Up or Ginger Ale. Ask for some volunteers and give each one an Alkaseltzer and about 4 or 5 ounces of pop. On the command “go,” each volunteer puts a tablet under their tongue and fills their mouth with pop. Tell them not to swallow the pop or tablet. (It won’t hurt but might not taste too good). The idea is to hold the mix in your mouth as long as possible. It will fizz and fill the mouth and will be hard to hold in. Make sure you have a bucket for each volunteer to “spew” into because that’s inevitable.