Run the garbage disposal, clearing it of any loose food.
Put a few ice cubes and water in the garbage disposal and run it. The ice cubes will help loosen more material in the disposal.
Place 1/2 cup of baking soda in the disposal. Pour 1 cup of vinegar down the disposal. This will cause a reaction and it will start to bubble. Let the baking soda and vinegar soak for 10 minutes.
Bring a large pot of water to a boil. Slowly pour the large pot of boiling water into the disposal. Start the disposal and let it run for a minute or two.
Take off the rubber splash guard in the drain, if you can. Scrub it with an old toothbrush, hot water and dish soap.
Scrub the drain with the same toothbrush, hot water and dish soap. If you can, place the rubber splash guard in your dishwasher for a deep cleaning.
Put the rubber splash guard back on the drain.
Place a few citrus peels in the disposal and run the machine. This will give the disposal a fresh smell.