Window covers

I used static tint once and it'd be good if you needed to be able to remove it and put it back up easily (fairly)

Black towels and velcro at walmart does wonders and can be taken down in the daytime.

I used cardboard and newspaper for a little bit, but that was a pain in the ass to put up/take down. I ended up making some curtains and stringing them up with some old clothes line. That way they're always there, but if you need to move your carhouse you can just slide them aside.
I guess it depends on the size of your vehicle, but it really doesn't take much fabric. You can usually find solid prints for as cheap as 2-3 bucks, then you can just hand sew it if you don't have access to a sewing machine.
I got lucky and found some insanely inexpensive pink fabric covered in odd looking bunny rabbits and melting carrots, that was apparently leftover from Easter time. Still confused as to how that never sold out...

On my van I cut insulation board and painted it black...the fit is so tight it just pushes into the window sill with no attachments...easy to remove for driving and totally private at night.

In my old Dodge tiny rv,I used this,to keep the cold out,in the winter,and the cold in,in the summer, yeah it cost,along with the tape,but I stayed comfortable ! http://www.westsidewholesale.com/re...3_a_7c713315&gclid=CNuThuag27MCFUOK4AodA0YARA

and you'll feel like you have your place,wrapped in "Tin Foil"...............lol