Lay a drop cloth outdoors in a sunny location. Move the mattress outdoors to lay on top of the drop cloth.
Vacuum the mattress thoroughly to remove any surface dirt or crumbs.
Mix a solution of two parts white vinegar and one part water. For ease of application, put the mixture in a spray bottle.
Spray the mattress with the solution so that the mattress is wet but not drenching wet. Rub the solution into the mattress with a damp cloth or sponge.
Sprinkle the mattress with a light layer of baking soda – long known for its odor-absorbing abilities. You may see a bit of fizz as the vinegar interacts harmlessly with the baking soda. Work the baking soda into the mattress with the cloth or sponge and let the mattress dry in the sun, which should help kill any remaining germs and help the mattress dry faster.
Prop the mattress on its side, supporting it with a heavy object, to dry thoroughly if you have cleaned both sides.
Vacuum the mattress again to remove any residue.
Prepare to repeat the process once or twice more, depending on the severity of the stain and odor.