Fill a spray bottle halfway with white vinegar in its pure form. Diluting the vinegar is not necessary. Vinegar is a much better cleaning agent as compared to bleaches and detergents or liquids because of the fact that it does not contain any harsh ingredients and there is no immediate wear and tear. Liberally spray the affected areas with vinegar from the spray bottle.
Use a cleaning sponge to wipe clean the made affected parts of the beach chairs. Be sure to work on one chair at a time. Wipe off as much of the white vinegar as possible.
Add a few drops of gentle dish cleaning soap, one tablespoon lemon juice, one tablespoon baking soda and a gallon of hot water to a large bucket. Thoroughly stir the contents of the buckets to form a uniform mixture. Allow time for any foam that accumulated on the surface of the mixture to properly settle down. Wash down the beach chairs affected by mildew with this mixture and then rinse the chairs. Be as thorough as possible.
Leave the beach chairs in the open so that the sun and air can completely dry them off. Keeping the chair in a shaded area with very little air will result in the mildew problem coming back.