Many commercial drain cleaning products are available, which can be used to eliminate the smell, but most of these contain harsh chemicals which can be harmful to you and your pipes if used incorrectly. The use of these cleaners should be a last resort.
Natural home remedies
Several natural remedies are available for eliminating this bad smell. The first step should be simply running lots of hot water down the drain. Many times this washes away the offending matter and solves the problem. This step should be a part of your normal kitchen routine at least once a week as it will help keep the problem for starting. A disposal can compound the problem because it reduces food scraps to fine particles, which can more easily be trapped in the recesses of the drain. For sinks equipped with disposals, bad drain odors can sometimes be cured by tossing a cut-up lemon in the disposal and grinding it up.
One suggested cure for the bad odor problem can also help speed up sluggish drains. To try this technique, simply pour ½ cup of baking soda in the drain and follow it up with a cup of vinegar. The chemical reaction between the acid of the vinegar and the alkaline baking soda produces a foaming action, which loosens the stuck particles of food and bacterial buildup and preparing them for flushing down the drain with a follow-up hot water rinse. On rare occasion it may be necessary to disassemble the drain plumbing and manually remove the sludge accumulation. Wear rubber gloves for this messy job. A dish washing detergent is strong enough to clean the pieces. Be sure to scrub any rubber gaskets and parts completely because rubber is a good home for bacterial growth.