The bottle is then handed to them, when the beer spills all over the place.

Preparation: You need

A packet of cigarettes.
A full bottle of beer.
A beer mat.
Scissors.
A fast pair of running shoes.

Method: Take the plastic wrapper off the cigarette packet and cut a circle just big enough to cover the rim of the bottle.
Wet the rim and stick the plastic circle on top of the bottle.
Place a beer mat on top of the bottle and holding the beer mat in place, turn the bottle upside down.
Carefully remove the beer mat and the plastic should keep the beer inside the bottle.
When your friend returns, it will look like the beer is defying gravity.
While they are still amazed, ask them to take a seat and hand them the inverted bottle.
Tap the bottom of the beer bottle gently and run as fast as you can as your friend gets soaked with beer.