dude that sucks.
being its a legal issue means they will most likely watch you piss.
i would go to urineluck.com / spectrum labs and check out xxl carbo drink and refrain from herb and drink a shit load of water.
i have also heard that a drink called magnum is trust worthy.
not much help man im sorry but being watched kind of screws you.
check out that site.
i have read that some have used the whizzinator or the urinator while being observed.
if your not watched or can get them to turn their back i would sub with a friends clean sample but that might not be an option unless you let them watch for awhile and dont piss, maybe tell them you got stage fright or something.