When sleeping in the car I had to take measures for covering the windows. The rear window has a roller blind, and the driver-side rear window (over the kitchen) has silver horizontal blinds. The windows at the rear seats I covered with two hanging-down organisors, one at each side, which also provide space for putting some odds and ends there. The front window was covered by a black blanket. Only the very rear passenger-side window did not have any cover.
I fixed that now: another set of horizontal silver blinds.