Ever Filling Glass

On your table is a glass of milk, take a few sips and drink it empty. Keep your hand there for a moment and within 2 seconds, the glass is again bursting with milk. You can smooth drop and your assistant comes along. Your assistant is drinking the milk. Again grasp the glass and invents a second hand and again the glass full. Then a stage manager runs alongside your magic table and drinks the glass empty. . . enfin you can imagine what will happen here.
You can empty a glass and within one second full conjure covered by your hand or under a cloth. Very easy to use, beautiful on stage and great for comic relief.