This is a prank that everyone should know. Whether you want to have a good ol' laugh with your mates, or you just wanna turn their drink upside down and piss them off.
Step 1: Fill Up a Glass With Water.
Step 2: Place a (kinda) Flat Plastic Bag on Top.
Step 3: Hold Down the Bag Tightly Around the Sides.
Make sure there are no folds or bends while securing. DO THIS PART IN A SINK OTHERWISE EXPECT ALOT OF CLEANING UP!
Step 4: Quickly Turn the Glass Upside Down.