Fill your washing machine with hot water. Thoroughly mix in your regular amount of laundry detergent plus 1 cup of bleach, white vinegar or baking soda. Caution: Do not use bleach with colored towels.
Stop the washer after it fills and add the stinky towels. Let the towels soak for at least 30 minutes.
Turn the washer back on and let it complete the wash, rinse and spin cycles.
Dry the towels in the dryer.
Launder the towels again if the odor persists. Use your laundry detergent plus a different additive -- bleach, vinegar or baking soda -- than the first time.
Dry the towels outdoors in full sunlight. Sunshine helps remove odors.