First, separate your whites from any other items in the washing machine and add 1 cup of baking soda along with the usual laundry detergent. For particularly dingy or stain-ridden sheets, you can also pre-soak them in a mixture of hydrogen peroxide and cold water for 30 minutes before washing. If you’re looking for an eco-friendly option, hang your sheets out in direct sunlight to bleach them naturally. Finally, consider adding a fabric brightener to the wash for extra crispness and shine.