By drug test, I assume that you mean a test screening for pot or cocaine. Pot: THC residude gathers in your bodies fat cells, so if you are fat it takes longer to get rid of it. Quick answer: Note, this is dangerous!!! Drink lots of water, until you are urinating a very clear fluid. This flushes your system out. It is dangerous to drink large quantities of water quickly. It affects the Sodium/potassium levels in your body. But by drinking water you temporarily flush out your urinary tract. You must continue to consume and pass water to maintain the clean effect. Also, some labs test the weight of your urine to determine if you are flushing.. . I do not know a lot about cocaine, except that for occassional users it leaves the body within 24 hours.. . Best answer is to not use any illict drugs.