You should clean your retainers multiple times a day to make sure they’re clear of food. You can do this by rinsing them off with lukewarm water and also brushing your teeth after you eat. Keeping your teeth clean helps to keep your retainers clean by preventing bacteria from transferring onto the retainer.
To clean your retainers, use mild dish soap and a soft-bristled toothbrush to brush the retainers. Toothpaste can be abrasive and scratch the retainers. You may also want to use a cotton swab to clean out any small areas the brush can’t reach.