What to do if i have a drug test in two days, what works best at gnc?

Nothing: There is nothing commercially available that will help you beat a drug test, and no ethical physician would or should tell you even if there were. What to do is to not use illicit drugs when such use puts you at risk - this is the definition of having a drug problem. Modern methods of drug testing will detect pretty much every potential technique for beating it. See your health professional.