Move the chair to a shaded area out of the sun. Spray the chair with water from a garden hose to loosen surface grime.
Fill a 3-gallon plastic bucket with 1 gallon warm water. Add 1 tbsp. liquid dish soap to the water. Thoroughly mix the solution to dissolve the dish soap.
Dampen a nonabrasive sponge in the soapy water. Sprinkle 1 tsp. baking soda on the sponge to help remove stubborn dirt.
Scrub the entire chair with the sponge. Wipe down vinyl slats, chair arms and legs. Frequently rinse the sponge with water from the garden hose to prevent reapplying grime to the chair. Apply new solution and 1 tsp. baking soda to the sponge after each time you rinse it.
Rinse the chair with water from the garden hose. Allow the chair to air dry.