His only hope is to use someone elses or to drink gallons upon gallons of water and pee out straight water, he can take a b2 and creatine supplement also so its not so obvious he diluted his urine.Not sure there is much your friend can do about their own urine. Not much time. Get some urine from someone you know is clean. Hopefully it's not one of those tests where the techs are in the room with you..
GL!