This is a rather uncomfortable but passable method of substitution that I used. As I am 17, my mother still drug tests me whenever she thinks something is up. The night before I had been using coke and marijuana, and DXM two nights previous. One of my friends that was cutting up the coke left a tainted pocketknife in the car my mother found.
As she took a ride to the local pharmacy to pick up the home test, I called up my friend who lives really close, I knew he was clean. I though having him piss in an insulated cup would work, but the temperature decreased sooner than I expected, and time was running out. My mother always picks the bathrooms for the test, so no luck hiding it in my bathroom. She also might tell me to wait a few hours before testing but keep a hawk's eye on me. I remember seeing Pulp Fiction and hearing the story about the guy sticking the gold watch up his ass for several years while a POW in Japan. So I cleaned out one of those hotel size shampoo bottles, poured in the piss, dumped the rest out of the coffee mug, and stuck that miserable hunk up my ass.
Sure enough, mother checks every bathroom for evidence and gives me the airport security routine. After finding everything clean, she gives me the cup and assigns the bathroom. After having the bottle in my ass for over half an hour, I remove and empty contents into test cup. Temperature is at a nice 96 degrees farenheit, and test results are all negative.
