Place a coin on any table that is not glass. Say that you are going to make the coin pass through the table, and then place your glass upside down on top of the coin. Cover the glass with a paper towel or napkin that covers the entire glass so that other people can't see the coin or the glass.
Close your eyes and announce that you are concentrating on the coin so that you can make it pass through. Open your eyes.
Play the trick one of two ways. You can act immediately as if something is not right, check under the table, and then act confused about why the trick hasn't worked. Or, you can excitedly pick up the glass as if to show that the coin is gone, and then appear shocked that it's still there.
Pick up the glass either way, and then, staring at the coin and diverting your audience's attention, allow the glass to drop into your lap. Place the paper towel, which should still hold the glass's shape, over the coin.
Announce that you're going to try a different method. Concentrate momentarily, and then smash your hand on the paper town and make it appear as if you have pushed the glass through the table.
Pull the glass out from your lap and announce that you were supposed to make the cup go through the table, not the coin.