Take the fabric covering off the couch, if your couch comes with a fabric covering that zips up over the couch cushion.
Wash the covering using strong detergent and the hot water setting on your laundry machine; wash two or three times if needed.
Spray the cushion, which may or may not include the covering, with a mixture of one part white vinegar to one part water in a spray bottle. Spray the entire affected area, then allow to dry in the sun.
Sprinkle baking soda on the affected area if the odor remains. Allow the baking soda to absorb the smell for 15 to 30 minutes, then use a vacuum to remove the baking soda.
Mist the couch with a natural air freshener. Pour eight to 10 drops of lemon essential oil into a spray bottle that contains 1 cup of water and mist your couch as needed.