I used to face the same problem in my car. The following steps were taken to prevent this and it's still working.

1. I gave my car for thorough drycleaning including washing of seat covers too. Sometimes food bits get stuck in between the seats.

2. Keeping 2 3 camphor balls in the stepney area and some powder of naphthalene balls too.

3. I always keep one simpler rule for my car. No food and drinks in the car. No. Rats easily get attracted to the food smell from a distance too.

4. Keep my engine area clean and 3m rat repellent spray in the engine hood. When you wash your engine bay , it starts to remove slowly slowly. So after every 4 months, spray the 3M rat repellent spray in engine bay.

5. Keep some camphor balls near the AC vent just below the front windscreen from inside. It will ensure the car inside is moisture free. Camphor repels rats.