Run a small amount of water in your garbage disposal so it's wet.
Measure 1/2 cup of baking soda and pour it into your garbage disposal. Follow this with 1/2 cup of white vinegar. Allow the combination to sit and foam in your garbage disposal for 15 minutes. The vinegar and baking soda mixture will work to dissolve any grease or small food particles creating odors in your garbage disposal.
Pour boiling water down your garbage disposal to rinse away the baking soda and vinegar mixture, as well as dissolved grease and food.
Slice four lemons into quarters. Place the lemon quarters into your garbage disposal and run them through. The lemons and lemon juice cut any remaining grease, clean out the garbage disposal and remove musty odors.