Terry from Winnipeg, Manitoba has a bad smell coming out of his sink garbage disposal unit that he can't get rid of.
Don't try to kill the smell with bleach. That will kill the smell, but it will also kill your graburator because the bleach will eat at any rubber or fiber washers. Look for an enzyme cleaner. Enzymes are actually bacteria, and when you put them into the garburator and let them sit for a while they will go to work on digesting any organic matter that is stuck in the cracks of the machine -- eliminating the source of the smells. Enzyme cleaners are the best at removing smells from anything because they keep eating until there is nothing left to eat and the problem is gone.
The catch is that they are hard to find because they are generally more expensive than other cleaners, have a short shelf life, and never get the big publicity that you see for other cleaners. Occasionally you will find them at the renovation centre, but you can often find them at pet stores precisely because they are non-toxic, environmentally friendly, and very effective at removing odors from organic sources.