some real silly ideas in here that would likely land a person in jail real fucking quick! if you are trying to scam someone, really no better way than selling fake drugs. you could go to the old tried and true ghetto way of passing macadamia nuts off as crack cocaine. there is also the suburban white boy method: trying to pass off wizard smoke or any of the countless other synthetic cannabis products off as the real thing to naive youngsters. the downside to this kind of activity is less likely to be police involvement, but a much higher chance of physical injury, particularly if ripping off hardcore drug addicts.
i remember this guy in high school, lets call him chris. what chris did was buy some incense, not the stick ones, the more solid cone variety. if i remember right, this particular variety was dark black, and on the softer side, kinda like a hard putty. it smelled like real pungent flowers. he sold this shit to people as "opium"!
who the hell smokes opium anyways these days, so that should have been a red flag right there. either that, or smoking something that must have caused a tremendous amount of damage to the lungs of the dummy that fell for it in the first place!