In Ontario, Canada, riding a bicycle on the road is considered operating a vehicle, and so a DUI is possible. I have never personally gotten on or known anyone who has, though. But I am not a memebr of the XXXtreme Blackout Drinker Club.
I actually tend to stay away from booze and rely on the devil's herb to get intoxicated. The only problem when riding on weed is going too slow and/or getting lost. And paranoia.