The only things that can improve your body's ability to clear THC metabolites are aerobic exercise and soluble fiber to a lesser degree. Niacin is a myth. Also, niacin is a water soluble vitamin which means that your body doesn't really hold on to niacin for very long. Fat soluble vitamins such as A & E will build up in your body.Energy drinks will not help you pass a drug test unless you drink about 48-64 ounces of them on the day of the test and this would be considered the dilution method. The extra fluid intake would dilute the THC metabolites in your urine on the day of the test. You cannot clean your body with energy drinks. If someone passed and they were taking niacin, it is mere coincidence. Any advice that starts off "my friend" or "my neighbor" or "my great uncle" "or this guy in my study hall" should be taken with a grain of salt.