Try taking aspirin a couple hours before the test. One study suggested that taking 4 aspirin 4 to 6 hours before the screening can mess with the test, EMIT. Don’t worry, 4 aspirin in a single serving will leave you fine, albeit a little light-headed.
Don’t waste your money on commercial products that disguise or clean urine. There’s no evidence that these products work. On top of this, they’re expensive, and many of the ingredients are simple diuretics, which you can purchase or make for far less cash. It’s pretty safe also to assume that drug testing companies are trying just as fast to come up with ways to detect these substances as manufacturers are coming up with ways to invent them. If you can, stay away.