So I didn’t get a great shot of “how”. But you place a squirt of whip cream on your wrist, about where your watch band would be, if you didn’t use your phone as your watch.
Then you hold your arm out and clap your hand pretty hard. You have to play with the direction of your hand, and how you hold your other arm, to get the whip cream to fly.
The object is to pop it out, and have the other player catch it in their mouth.
If it gets too difficult there are other ways for getting it in the mouth . . .
Tips, Whip cream fresh can and really cold. Stack the blob on your hand with a small dollop on your skin, then a fatter dollop on top of that. Make sure the other player is bent down and can move around sort of crab style. Have fun. Have a dog on hand to clean up.
Please ignore that it is summer, and the boys are wearing long sleeves, jeans and sweatshirts.