Drugs are ingested and then come out of the system as metabolites. Drinking more water will help your body produce metabolites that aren't tainted by drugs.
[header] How to pass a urine drug test [title] Drink lots of fluids before the test. [step] Also called flushing, this method remains one of the easiest, cheapest, and most successful ways to get a false negative on a pee test. Pee tests do not measure the amount of drugs in urine; they measure the amount of metabolites in the urine.