Step 1: Stuff You Will Need:
This stuff you will most likely have at your house:
-a piece of THIN cardboard (you can cut one from a cereal box, and it will need to be bigger than the cup's lip
-some towels (optional, it is nice for clean up)
Step 2: Step One:
Fill the cup with water half way and put in some ice.
Step 3: Step 2:
Step 4: Step 3:
Step 5: More Ideas
Another thing you could do is do this a bunch of times on an entry way into a kitchen or some other flat surfaced location. The victim would be trapped then because they can't just pick all of them up. They would have to get a piece of cardboard and take out every single one out of the entry way.
Thanks for reading!