Here's a suggestion to beat the piss test: Stop smoking dope.
While it may be psychologically habit forming, it is not physically addictive. If one has the will to quit, and is not a weak whiny DUmmy, even someone who has smoked dope heavily for most of their life can just stop, not look back, and never miss it again.
Trust me, I know of what I speak.
Nuff said about that.