Car Living: black out curtains

Cheapest way is buy two black pillow cases for $1 at Dollar Tree.

Shove the edges of the pillow case into the rubber sealing around the inside rim of the window.
Windows slide up and down without interference.

Mosquito netting can fit between the curtain and the window. (For $1 worth of tulle fabric. See: http://alchemytheory.blogspot.com/2017/07/life-hack-car-screen-window.html)

The rear windshield can be covered with two overlapping sunshades. Fit the metal edges of the shade into the ceiling wall for a tight spread.