I have used Softscrub with Bleach.

bleach can damage vinyl and cause it to turn brittle. Try a solution of murphy's oil soap, followed by a damp rag soaked in old fashioned brown/red Lysol solution (available at most hardware stores, the old style disinfectant stuff that you mix with water). That will discourage the mildew from coming back. If the upholstery is textured, you can use a soft brush to scrub.