Garbage disposals will sometimes emit a foul odor, typically caused by food particles that have not been completely flushed through the drainpipes. To get rid of the odor, first put a stopper in your sink. Fill the sink halfway with lukewarm water. Add four tablespoons of baking soda. Pull out the stopper and turn on your disposal so the sink can drain. The water will flush out the disposal and remove any trapped food particles. The baking soda will absorb any remaining odors.