I have a 98 honda crv. I live in Las Vegas and when the temp outside is over 100, like today, there are terrible strong fumes like strong dry cleaning fluid in the front right area of the car. This starts after the AC has been running for about 10-15 minutes. If you run the car longer than this, the fumes get worse inside the car, nauseating. I have had a mechanic tell me to replace the gas cap, but this did not work. This happens when the gas tank is empty or full or in between.
If it is a sickening sweet smell you might be smelling anti freeze. The heater core counl be leaking and it is on the right side below the glove box. Feel the carpet in that area and check if it is damp. If it is, then you need a new heater core.
Take it to an auto parts chain store and ask them to read the “codes” for free. They will hook up an electronic device to a connector under the dash and “read” any stored malfunction codes. Write the codes down in “P0123” format and post them here. If there are any codes relating to the evaporative emissions system you might have something like a stuck open purge valve that is letting gas fumes get sucked into the cabin.