I use to use CERTO
you can find it at any ralphs or longs/market...
its in the Jello section, its basically fruit pectin that coats your stomach.
look for the big blue box (cause there is 2)...dont get the small yellow one, its not enough.
take the first packet 2 hours before your test, mix it with about 1/3 water. pee as many times as possible in the next hour. then 1 hour before your test take the second packet and do the same thing, your piss should be clear by the time you know its working...if anyone ask's why its clear simply answer "i drank a lot of water cause I knew i was going to have to pee" simple as that.
worked 100 percent of the time for me outta 20 tests every month when i was a young kid on probation for transporting cannabis. haha. never stopped burning!
(oh ya you dont want to eat any sugars or hardfoods in the morning/before your test, cause they will break up the pectin in your stomach)
AFTER your test you wanna eat immediately to get that crap out of your stomach...it can make you kinda weasy and sick if you dont flush it out within 4 or 5 hours prior to testing.
best way for sure, and it only costs you about $5.00