The heat from sunshine , esp in FL is a constant.
The best way to get rid of it is to reflect it away , a glass that absorbs the heat will feel warm to the touch and pass heat into the cabin.
Out simple system is cloth window covers created so they can be snapped in place either inside or outside.
Cruising they can be snapped in place quickly , for comfort or privacy , when the boat is unoccupied they snap on inside to reduce sun damage and not get blown off in a hurricane.
Marina bound folks can have covers made from RV windshield style material that blocks the sun but allows viewing from inside.,,,, However if you light up inside at night , you are on display.
Marina Plan B is reflective mirror foil stuck on outside , for the Bubba cop sun glasses look.
Plan C is "warm shades" insulated pull or roll down shades that are a great help if air conditioned or heating.