Place the towels in the washing machine. Avoid overloading the washer with too many towels because they may not become entirely clean, which will cause the mildew smell to remain.
Add your regular detergent to the washing machine. Add 2 tbsp. of baking soda to the washer. Wash the towels in hot water.
Pour 1 cup of white vinegar into the washing machine during the rinse cycle.
Place the towels in the dryer immediately after you wash them. Dry the towels on the highest heat setting. Hang the towels outside in the sun or in your home if you prefer. Allowing the towels to air-dry will remove any lingering mildew smells.