Some trunks are machine washable. Check the care label to determine the proper way to clean them. If they can go in the washer, use the cold cycle and a mild laundry detergent to help keep them in good condition.That said, to extend the life of your trunks, it’s best to hand wash them. Use cold water and a mild detergent in the sink. Swish the swimsuit around in the mixture for a few minutes. Then, rinse well. Carefully squeeze the excess water out of the material, and allow the trunks to air dry.