If you want to prevent more of the sun’s heat from entering the cabin of the Tesla Model 3, the glass roof is a good place to start. Even if you don’t have the panoramic roof option, there is still lots of glass on the top of the Model 3.
Some Model 3 owners have expressed concerns about harmful UV rays entering the vehicle, and Tesla responded saying that 100% of UV rays are blocked, and 83% of heat transmission is blocked by the panoramic roof glass.
Tesla offers sunshades that are made of a lightweight mesh fabric and Tesla says it blocks two-thirds of the solar thermal load, but still allows light through.
Here is a review of the Tesla sunshade including unboxing and installation of the sunshades:
There are also many aftermarket options similar to the Tesla sunshade that are made of mesh fabric.
If you want a complete blockage from the sun passing through the roof, there is only one product currently available that does that.