Water Cup Prank

I wanted to play a prank on my sister, so I kept asking around. One of my friends told me this prank and now I'm going to tell you what happened when she did it.
I told my sister she had to try this challenge that I did with a friend, she willingly agreed. So I filled two water cups halfway full of water and told her to try to balance one on her hand palm down. But first I Showed her making it look easy but I lifting my fingertips up a little bit. After she mastered to having it staple on one hand tell them to put The water cups on both hands help them get it stable and then say you have to get something to finish the trick, then don't come back but get in a place where you can see them and they can't see you, now the only way they can get the water cups off of their hands is to spill them. Make sure you had this whole thing videoed so you can be sure to show other people.
When I did it my sister wasn't really mad she was just a little annoyed that that was all that the trick did, but be sure to try it on a little sibling it will really be hilarious.😍😍😍😍😍😍😍😍😍😍😛😛😛😝😝😝😝🤤🤤🤤👿👿👿