there are products in head shops that do it, or first of all it depends last time u smoked, hopefully it was more then a week and a half ago, drink alot of green tea and half a bottle of vinegar and u should be good, remember that you can always take another cuz u can say they made a mistake so it would be another two weeks with out bud but then u would pass for surely my friend was in the same situation and smoked a week and a half before and he was good