Crystal methamphetamine.
Seriously, drink lots and lots of water. The more water you drink, the less water your body retains. You've got to stay away from the soda like the plague.
Also, well, if you want to get drastic, then get your self a plastic suit (or some large trash bags), a sweat suit, a toboggan, some cough drops, a big cup to spit in, a jumprope, and a sauna and you can lose 10 pounds a night. I used to wrestle in middle and high school, so I know about all of the brutal weight cutting techniques. They work, although they'll leave you on the verge of death. So, I'd advise to wait until the last week or two to implement those kinds of things, if in fact, you are that determined to win.