This effect is extremely simple to perform, very effective, and appropriate for any type of show.
There are three clear tumblers each covered by a different colored cover. Two spectators freely select two of the tumblers leaving you with the third. There is no force and they can change their minds as often as they wish. The tumblers they select are empty and they one they left for you is filled with currency, silks, etc ...
Once you are familiar with the effect you will discover several presentations. You can have any tumbler "full" or "empty" entirely under your control.
Supplied are three gimmicked velvet bags. You supply the 3 clear glass or plastic tumblers.