Typically, odorous drains indicate the presence of something emitting a foul odor. This could be food, grease, gunk, or anything else that made a home in the drain. What gets caught in a drain can provide a home for a variety of organisms, which can contribute to the odor.
A good old-fashioned drain cleaning is our recommendation. We recommend hiring professional Fort Myers plumbers to do the job because they have equipment that allows them to clean your drains without damaging them.