No one likes having a smelly kitchen. Have you ever had a moment when you cleaned your entire kitchen, looking to eliminate odor, only to find that odor was coming from your kitchen sink drain? It's a frustrating occurrence, but can be dealt with quite easily.
Remove any debris in the sink drain. Run the garbage disposal if you have one. If not, remove the debris manually, if you can reach it. You may have to remove the sink trap (the U-shaped pipe beneath the sink) to clear out substances caught in the pipe.
Run hot water into the drain. This will kill bacteria that may be living in the drain. Depending on the temperature of the water in your house, you may need to boil water and pour it in the sink to kill bacteria. Be careful not to burn yourself on the metal parts of the sink; they will retain the heat from the water.
Throw a teaspoon of baking soda down the drain. Continue running the hot water during this process. Baking soda is useful for killing odors.
Pour vinegar, bleach, or lemon juice down the drain if baking soda and hot water don't do the trick. Be sure to ventilate the room and wear old clothes if using bleach. Let the cleaning solution sit for 15 minutes, then run hot water again and check to see if the odor remains.
Purchase a heavy duty corrosive drain cleaner such as Drain-o or Bio-Clean's Bac-Out if you still have odor problems. These or similar products can be purchased from a grocery store or home supply store. Follow instructions carefully for your safety.