Yes, aluminum foil can be used over windows to help keep homes cool

[Old Crank]

5. The foil or other reflective device

works best when sun hits the windows.
Our previous house had windows facing north and south mostly. The west ones were shaded by trees.
At night when ever the sir temp was lower outside we opened the windows and sliding door and drew in cooler air with a box fan.
In the morning when the house was at its coolest and outside temps started to rise we closed all the drapes and windows to maintain the cool. Rinse lather and repeat.
You can dampen towels to put in the airflow from the fan to help drop temps if you are in a dry climate. Don't have the wet air drawn through the fan's motor.