Answer
First,the water stuck the match into the lemon wedge,so that it would stand straight. Then he lit the match and put it in the middle of the plate with the lemon. Then, he placed the glass upside-down over the match. As the flame used up the oxygen in the glass, it created a small vaccum, which sucked in the water through the space between the glass and the plate. Thus, the waiter got the water into the glass without touching the plate.
First,the water stuck the match into the lemon wedge,so that it would stand straight. Then he lit the match and put it in the middle of the plate with the lemon. Then, he placed the glass upside-down over the match. As the flame used up the oxygen in the glass, it created a small vaccum, which sucked in the water through the space between the glass and the plate. Thus, the waiter got the water into the glass without touching the plate.