The absorbent upholstery on couches makes them targets for persistent odors. However, you can combat odors with common household products. Keep couches clean, and vacuum them weekly to get rid of odor-causing substances. Put a blanket or washable slipcover on the couch if you have a pet or children that aggravate the problem.
Put a fabric softener sheet inside an envelop, and slide it under a couch cushion.
Sprinkle baking soda on the upholstery, and leave it overnight. Vacuum up the baking soda the next day.
Mix 1 part white vinegar with 3 parts water in a spray bottle. Spritz the upholstery on the couch. Do not saturate it. Let it dry.
Sprinkle salt under the cushions of the couch. Vacuum it up the next time you clean the couch. Flip the cushion and sprinkle salt under the new side.
Spray perfume on cotton balls, and slide them under the couch cushions.