Here are some:
My 78 year old mother crossing the border into France let the ice melt in her refrigerated motorcycle side panels--and thinking it was Pom Wonderful - I drank 2 pints - er, uh, I mean bottles..
My hotel got my room mixed and accidently put my agent's centrifuge and blood for his Hemopheliac wife in my room. I assumed it was my special-order Charlie Sheen Tiger's Blood and drank it.
I didn't actually test positive, all 18 people, including testers and people who saw me take the drugs, have, in some way, zero credibility, and I like my credibility.