Some diy overnight face masks for dark spots are as follows: Apple Cider Vinegar Mask: Add 2 tablespoons of apple cider vinegar to a cup of water and soak a cotton ball in the mixture. Apply the soaked cotton ball to your face and leave on for 15 minutes. Rinse with warm water and pat dry. Baking Soda Mask: Mix 1 teaspoon of baking soda with enough water to make a paste. Apply the paste to your face and leave on for 15 minutes. Rinse with warm water and pat dry. Honey Mask: Mix 2 teaspoons of honey with enough water to make a thick mask. Apply the mask to your face and leave on for 30 minutes. Rinse with warm water and pat dry.