Actually I'm not trying to be insulting... someone actually did just that in an attempt to fool a breathalyzer. It didn't work:

TORONTO -- An accused drunk driver tried but failed to foil a police breathalyzer after stuffing his mouth full of feces....

Arrested Sunday after his Ford pickup was pulled over on a highway just outside of Barrie, the 59-year-old driver was loaded into a cruiser and taken to a police station for testing....

After arriving at the station, (Sergeant James Buchanan) said the man grabbed a handful of his own waste "and placed it in his mouth, attempting to trick the breathalyzer machine."

It didn't work, Buchanan said.

Hat tip to the DUI Blog for this rather disturbing story on the lengths that people will go to in order to avoid a DUI. So how drunk do you have to be to not be revolted by the mere thought of eating your own crap? Suddenly my breakfast isn't sitting so well.