Clean white plastic lawn chairs with bleach and hot water. Spray the chair with a garden hose. Pour 1/4 cup of bleach into a pail of hot water. Dip the scrub brush into the solution and scrub the chair, using a circular motion. Allow the solution to sit for five minutes, then rinse with a garden hose. Place the chair in the sun to dry.
Use a Mr. Clean Magic Eraser on plastic lawn chairs of all colors. Rinse the chair with a garden hose. Moisten the Magic Eraser with water, then scrub the chair with the sponge. Use the garden hose to rinse off the soapy water. Allow the chair to dry in the sun.
Brighten dull-looking plastic lawn chairs with vinegar and hot water. Spray the chair with a hose. Pour 1/4 cup of vinegar into a pail of hot water. Use a nylon-bristle scrub brush to remove dirt and grime. Rinse thoroughly with a garden hose and allow to dry in the sun.