The reusable static-cling Window Blockout is a an alternative to baby blackout curtains. 

This is the perfect solution for babies and toddlers who need total darkness in their room to sleep and dream the night away. A completely dark room during sleep will help stimulate melatonin production (that magical hormone that helps regulate sleep/awake cycles ), be comforting for your baby, and help prevent early waking or late settling during summer and daylight saving.

The Window Blockout is made from 3 layers of material with a completely opaque inner layer to block 100% of sunlight from rooms. The outer layers of this baby window shade are white to seamlessly and stylishly blend in with your child's sleep space. The inward-facing side of the blind will block out the light, and the outward-facing side will reflect light away from your windows, helping to regulate the room