synthetic piss is legit, have used it with success.
I've also used and passed a few using Hydrochlorothiazide, a common blood pressure diuretic. Most of the "test clean" drinks you see at smoke shops just have herbal diuretics anyway as the actual working ingredient, but I don't really trust them and would rather go prescription strength.
I have a parasomnia sleep disorder in which I can become extremely violent in my sleep. I can't share a bed with anyone, or they may get seriously hurt, and several years of trying different therapies and medications did little but get me hooked on benzodiazepines.
Found that weed works great. Doesn't cure my problem, but makes it so I can fall asleep, and greatly reduces the quantity and severity of nighttime episodes. Once they improved I felt better about myself and didn't need the antidepressants, and could get off the benzos.
Even if you don't care much for the high, I don't think you'll regret it for sleep purposes.