I installed heat rejecting ceramic tint covering all windows that isn't the windshield. Reduces the glasshouse effect in a big way. For the windshield, I use the tried and tested silver foil reflector thingy.
also 'clear' ceramic tint on the front windshield does help (at least in my MS) in the summer in Houston
Texas law allows for the entire front windshield to be filmed/tinted with a “clear” un- tinted film that does not visibly alter or color the glass when viewed in natural daylight. ..