Don't get to close with the blow dryer burn your shit off.
But for real I knew someone that did this method they used a zip lock baggy of piss and everything.
Squeeze the bag and the piss came out the straw so it looks like legit pissing if they watch you do the test.
I've heard consuming a lot of vinegar will help but I've never had a drug test done nor can I confirm if this is legitmate, just something I've heard from stoners at my school.