Rinse the canvas regularly with your hose. Do this on a warm, sunny day when possible, as this allows the water to air dry quickly.
Mix a 50/50 solution of water and white vinegar in a spray bottle. Spray this over the waterproof canvas. The vinegar disinfects and deodorizes, plus gets rid of any mold or mildew growth. While mold and mildew are not typically an issue with waterproof canvas, the elements can sometimes build up if the canvas is subjected to standing water for long periods of time.
Mix 1 gallon water with 2 tbsp. laundry detergent. Dip a sponge in the bucket and scrub down the canvas to remove bird droppings and other residue built up on the canvas.
Rinse the waterproof canvas with your hose once more and allow it to air dry.