If you have a garbage disposal the odors may coming from food that is ground into a sticky paste on the inside of the pipe leading from your disposal to the diverter tee. Some warm water and 1 half of a lemon thinly sliced and ground up in the disposal every 3 to 4 days works well. Keep doing this until the odor goes away this will break down the food paste and leave your sink area smelling nice. If this is sewer gas this is potentially dangerous call a licensed master plumber to check it out.
Another remedy for stinky drains is one part vinegar to one part baking soda mix and let sit in drain for an hour or overnight. Good Luck Bill The Local Plumber Tustin, California http://www.TheLocalPlumber.com