If you’ve finally found a flattering swimsuit that you wish would last forever, you can prolong its life and shape by rinsing your suit after your day of swimming in cold water and then soaking in a sink or pail filled with one quart of water and one tablespoon of white vinegar for about a half an hour. Let it air dry. The vinegar will clean your bathing suit without making the fabric coarse or prone to stretching like a detergent will.