I remember reading a legit scientific paper (from like 1993) that said that visine (1 part : 9 parts piss) effectively lowers the detectable amounts of THC metabolites in urine.
It is definitely undetectable (neutral pH, no change in color etc.) but drug tests have probably advanced since then. I've used it twice and passed, but I mostly used it as a precaution and I probably would have passed anyway.
Sig credit: MC
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