How do you mask urine for drug test?

If you need to take a drug test, but you know you have THC in your system, the best thing to do is, and this is gross, drink vinegar. I have heard that this will flush the THC out of your system, but I'm not positive about that. Another thing, drink A LOT of water before taking the drug test. Sometimes if you drink enough water your pee will be diluted and nothing will show up on the drug screening.