az bound is right about the sewing. There are enough holes in the material that it sews fairly easily. Use heave thread and a denim needle.
Suction cups work fairly well, but the RV needs to be clean, as do the suction cups themselves. Road dirt and grit will cause them to leak vacuum and fall off.
Consider putting the shades on the insides of the windows. The shades will be easier to reach (no ladder necessary) and you can put them up regardless of weather.
We used snaps across the top of the windshield shade and suction cups along the bottom. The sides tuck behind the windshield trim, or you could put snaps there, too. The side windows are held up with snaps and Velcro. You can buy kits to set the snaps into the fabric. Use short screws to hold the other side of the snaps to the window frame. Sew one side of the Velcro to the fabric, and use self-stick Velcro on the window frame.
Check out our blog post
to see how we made our own sunscreens.