another piss test question

my friend and i smoke weed every day, pretty much all day. hes about 5' 10", 190lbs or so and has some fat but not a lot. hes gonna start getting drug tested weekly and needs to pass or hes getting kicked out of his house now thats hes 18.

what drink/pills would work best to clean him out? he refuses to use fake piss cause he thinks they're gonna watch him. does anyone have any suggestions on something to get thc out of your system in like a day?

any help would be appreciated...