sneaking pee into testing facility?

I have a drug test in a couple days and i need to figure out how I can sneak some urine into the facility without it being detected. I have a medicinal marijuana card but i’d rather not go through the entire process of talking to future employers about that so i’d rather just sneak in some urine from my fiancé and call it a day. I’m stuck on the how though. I have cargo pants that’ll have pockets big enough to hold it but idk about keeping it warm. Any ideas?

if it helps, i’m 6’3, 200lbs