Clean your strap in a large sink using a mild soapy, warm water and a sponge or soft brush. Once you’re happy that your strap is cleaned, you rinse thoroughly. Make sure you remove all traces of soap in and outside of your bag.
Finally, hang it out to dry outdoors or in a well-ventilated area out of direct sunlight. Your bag will both drip and air dry to finish up. Ventilation is the key to prevent the strap from being damp for too long.