After taking cocaine , how long does it take to go out from your system so it cant be traced by urine tests ? Metabolisim no doubt has a part to play , but there must be a general timescale . What about other drugs?
It’s probably safer to fill a specially made bag with someone else’s urine and hide it under your clothes, so even if someone stands outside the stall while you provide the sample they’ll think it’s yours. 
Which is precisely why many drug-testing facilities have someone stand inside the stall with you, to watch you pee, in order to make sure you don’t pull a stunt like that.
You’d need to keep it warm. Those cups have a temp gauge on the side.
I imagine that tests for government jobs, or high-power positions, do. But for the average Joe Shmoe going into some blue collar warehouse or clerical job, the company probably doesn’t want to pay too much extra money. The place I went to didn’t have anybody come in (and thank god… that guy was REALLY creepy. If I ever make a movie about my life, I’d have to cast Crispin Glover for that role).
Somehow I thought it was 24 hours… thank god I was never tested in my heydays:p
Can they do that? I don’t think I would feel very comfortable with some guy watching me pee.
Ahhhh… memories.
In the Nav, every once in awhile you have to submit a random urinalysis (back in the day, it depended on the last digit of your SSN).
In most cases, this amounted to you walking up to a urinal, with a Master at Arms standing next to you, staring directly at your junk, tapping his foot, saying “Come on now. I don’t have all day!”
In higher volume situations, there was this whole routine where six or eight guys would hold one arm in the air as they performed the required movements with the other arm, 1 foot back from the urinal, with the MAA at the end of the row watching everybody.
Boy it was hard to get started under such scrutiny.
welloso
Not to moralize, but if you really don’t want cocaine to show up in a urine test, how about not using cocaine at all ?