They ain't gonna find any detox drink. And what do you mean they're watchin you ?? Thats just bullshit. I dont think they can unless you're in jail or military. If they did I'd say "Hey lady I can't go with you starin at it. " Or "What kind of speciman do you want" If its a guy I'd shut the door then beat the snot outta him and say he touched me. I dont think they want that. I still say they cannot invade your privacy.
If you use someone elses sample, or a synthetic urine they're gonna test the temperature on the spot. You better be within range.