Plastic watches come in many colors and styles and have bands made of polyurethane with a flexible texture. The watches are primarily for general wear, and do not hold up well under extreme moisture or outdoor conditions. If you own a polyurethane watch that's dirty, clean it with basic household products. With proper care, most polyurethane watches last between 18 months and three years before requiring replacement.

Fill a bowl with lukewarm water and 1 teaspoon of liquid dish soap. Stir the mixture with your hand until soap bubbles form on top of the water.

Dip a terrycloth washcloth into the bowl until it's saturated. Wring the washcloth out to remove most of the moisture.

Spread a towel on top of a flat surface and lay the polyurethane watch on top of it. Scrub the band portion with the washcloth to remove any visible signs of dirt or stains. Rinse the cloth as needed in the bowl, but wring it out thoroughly before placing it back on the watch.

Wipe the face and back of the watch, using the washcloth, after you finish cleaning the band.

Examine all surfaces of the watch for tough stains that remain. Wet a melamine foam sponge in the bowl and wring it out. Rub the stains gently using a circular motion until you no longer see them.

Wipe the watch thoroughly with the towel to remove all traces of moisture from it.