I vote for jello
Just get the jell-o mix, make it in your glass and let it set. Or make jello cubes and put them in there and fill it with juice. OR!!!! A jello diffuser...That would be cool. I doubt it would work.
Maybe Jell-o's arch nemesis....Pudding. Brazillian Pudding! Probably would be too thick unless you water it down with milk or cream.