Pour undiluted white vinegar into a spray bottle. Undiluted white vinegar will kill severe mildew growing on your cloth outdoor furniture, according to Reader's Digest online.
Saturate the mildew on your cloth outdoor furniture using your vinegar spray bottle. Allow the vinegar to dry on the cloth surface for an hour or so.
Fill a bucket with hot water and 1 tsp. liquid dish-washing soap. Dip a scrub brush in the soapy solution and scrub the mildewed areas on your cloth outdoor furniture. Frequently dip the scrub brush in the soapy water to remove mildew and freshen the soapy solution on the brush.
Rinse your cloth outdoor furniture with your garden hose to remove the dish soap solution.
Spray the cloth again with straight vinegar, then place your cloth furniture in the sun to dry. Spraying the cloth outdoor furniture with vinegar a second time will prevent mildew from returning.