Urine samples are given for various reasons, often the reason is sports related. Of course nobody who takes a drug test wants to test positive, but unfortunately people do, sometimes they do without actually doing the drug they tested positive for, this is called a false positive. A common example of this is when Elaine on the television show Seinfeld tested positive for opium; she had eaten too many poppy seeds, and gave a false positive.
The answer to this specific question about methamphetamine (commonly found in the drug called Extascy), you can give false urine samples if you ingest the plant Ephedra. Ephedra is found in some dietary supplements, and it is a plant that grows in central Asia, among other places. It is considered a stimulant and as well as dietary supplements, it can be found in some over-the-counter asthma medications. The Ephedra plant contains ephedrine, and pseudoephedrine, the latter is in many cold medications, the day time kind.
For more information on false positives check this link out:
http://www.passyourdrugtest.com/false-positives.htm
For more information on ephedrine look here:
http://www.ephedrine-ephedra.com/pages/what_is_ephedrine_1234.html
