There was some car which used a small solar panel to pass fresh, cooler air into the cabin during sunny days. This both made the car more pleasant to enter and lowered the initial AC surge. I don't know if it also trickle charged the starter battery so it never could get completely depleted from just standing for longer periods. Both these things seemed worthwile.
The 2010 Prius IV had this as an option - one of my favorite cars due to low maintenance (the lowest maintenance visits per year for its era). The solar panel air vent circulation is a nice feature (even if slightly gimmicky) and I suspect extends the hybrid battery life as well by preventing some marginal battery heat death while parked.
The newest (2023+) Prius brought back the solar roof as an option - and this time it charges the battery (albeit marginally / but not bad for those that drive minimally).
A more practical solution is to leave the windows slightly open so the hot air escapes.
There are places where a marginally open window will invite vandalism, or rain, or bugs, or smoke and bad smells.
Not practical if rain is forecast.
The car already has a rain sensor so it can close the windows automatically. I do believe some VWs already do/did that.
My car has that to activate the wipers. To say it works reliably is to lie.