Lemon juice: Dab freshly squeezed lemon juice on the sun spots twice a day. You can also apply it as a pack after mixing it with one tablespoon of honey. Leave it for 20 minutes before washing it off with cold water.
Buttermilk: Apply pure buttermilk on the spots. Wash after 15 minutes. It will help lighten spots.
Red onions: Apply red onion juice on the spots thrice a day. This makes the spots fade