1 day? There is a slim chance you'll pass, I hate to say.

But drink water, lots of it, and get a hold of some green tea if you can. Cranberry juice like mentioned as well. All 3 of those are great cleansing agents to get toxins out.

I'm guessing it's a urine test.

If it's a blood test, you're screwed, if it's a hair test, you're even more screwed, and the only way to pass a hair folical test is to shave off every piece of hair on your body. They can do drug testing from your eyelashes, eyebrows, and pubic hair.

Keep in mind there is such thing as water intoxication. There was a sotry awhile back where a girl died of too much water. Your stomach can only hold about a litre of water at once, so just be careful not to overdue it.