The thing about drug tests that most people don't tell you (or that most don't know) is that your body doesn't have to be 100% clean in order to pass. Most tests have a threshold (usually 50mg/dl for THC) that has to be exceeded before your test will have a positive result. THC is stored in your fat cells so it is impossible to flush it all out in a short amount of time. All you want to do is water down your urine so that the THC level is below that threshold. Unfortunately if your urine is too watered down your test can also come back as positive, or they can make you retake the test. They usually measure creatinine levels and electrolyte levels in your urine to see if it is watered down, so here is what you do to trick the test:

1. Go to the store and buy several 1 gallon jugs of gatorade (flavor doesn't matter). Instead of drinking straight water, start mixing water and gatorade 50/50. The extra electrolytes in the gatorade will help keep your body's levels constant while you increase your fluid intake.

2. (optional) Go to GNC or any other health supplement store and buy a bottle or Creatine Monohydrate. It's cheap (usually around $20 for 1000g) and very safe. Mix 1 teaspoon (5g) into your water/gatorade mix 3-5 times a day in the days leading up to your test. This will help the creatinine levels in your urine remain constant.

3. On the day of the test, wake up several hours prior to your appointment and start drinking your water/gatorade mix. Try to urinate several times prior to taking the test to make sure THC levels in your urine remain low. THC is most abundant and the beginning and end of your urination. Urinate in the toilet for several seconds, fill up the cup, and then finish urinating in the toilet.

4. Don't smoke again until you know for sure that you passed. If they confront you about have a watered down urine sample, simply tell them that you've been having problems with cramps so you've increased your water intake. The worst they usually do is make you retake the test, which just gives your body more time to cleanse itself.

How do I know all this? I'm in the Army and I've been tested monthly for years now, and I've never been caught.