Dilute your urine by drinking a lot of water and then take vitamin B12 to give your urine color. Practice the dosage because if you take too much your piss will be a neon yellow. Stay away from store bought drinks, the main ingredient is Pectin and that can be bought off the shelf for a 1/10th of the price.
If you fail the piss test, ask for the percentage for false positives. I failed a test once and it turned out it was only 82% accurate. I was able to then claim a false positive and retest.
