Properly timed poison.
I'd say get to the match a little early and while you are putting your things down attach a device to the underside of the opponents chair. When the match starts ask the TD what the beeping sounds are coming from your opponent side.
hahaha..nyc one Sangwin.....
Superglue all his pieces except his knight to the board.
We have the same avatar.
1. g4 e5 2. f3 Qh4 ++ Pretty sure you won't find a faster checkmate than that 2 mover. Of course you didn't say "checkmate"; you said "win a chess game". So I suppose even faster would be to have your opponent instantly resign!