Wonder Milk Glass

A glass full of milk is emptied in to another glass yet the first glass is still full. For the climax you give the spectator a straw and tell them to sip the air and as they do the milk miraculously vanishes from the glass in your hand.
Another nice trick with this magic milk glass is "The Milk in Newspaper Trick" where again a full glass of milk is shown, and a sheet of newspaper is rolled into a cone. The milk is poured into the cone; the level of milk in the glass is actually seen to reduce. The cone is ripped up and shown the milk has vanished.