It is surprising that garbage disposals don't become smelly more often when you consider what goes through them. The very action of the blades is likely to throw ground up food against the walls. To prevent odors, simply run orange or lemon rinds through the disposal with a few ice cubes ever week or so.

Even if you already have an odor problem caustic cleaners are not necessary. Most homes already have products on hand that will effectively resolve the issue.

Mild Cleaning

The easiest way is to fill the sink about 2/3 full of warm, soapy, water then turn on the disposal and let the water drain through with the unit running. This will create a whirlpool action and flush food particles that may be clinging to the sides of the disposal walls down the drain. Turn on the cold water for a minute or so after the warm soapy water has drained to finish flushing everything clear.

Tougher Odors

If you have an odor problem that isn't resolved with the soapy water, try pouring 1/2 cup of baking soda into the disposal unit. Let it sit for about 30 seconds, then add an equal amount of white vinegar. You may want to insert the stopper in both sinks while the solution is bubbling. When the fizzing action dies down, flush the system with a medium sized pan or teakettle full of boiling water. Follow up by running cold water through the disposal while it is operating to wash everything out the drain.