Failed test. If such a thing needs a good test, we as public can straight go to GPT and get the infos...
Here are the answer by ChatGPT 3.5:

Sleeping in an electric vehicle (EV) is not recommended and can pose serious risks to your safety. Electric vehicles are designed for transportation, and their interiors are not equipped for overnight stays or sleeping.

Here are some reasons why sleeping in an electric vehicle can be dangerous:

1. Limited Ventilation:
Electric vehicles are not designed for extended occupancy, and ventilation systems may not be sufficient for long periods. Lack of proper ventilation can lead to a buildup of carbon dioxide, which poses health risks.

2. Battery Drain:
Using the vehicle's systems, such as heating or air conditioning, while parked can drain the battery. If the battery is depleted, you may not be able to start the vehicle when needed.

3. Risk of Carbon Monoxide Poisoning:
Running the engine or using a gasoline-powered generator inside the vehicle for heating can lead to carbon monoxide buildup, which is extremely dangerous and can be fatal.

4. Temperature Extremes:
Extreme temperatures, whether hot or cold, can make the interior of a vehicle uncomfortable or even unsafe for sleeping.

5. Emergency Access:
In case of an emergency, being inside a closed vehicle may hinder access and evacuation.

If you need to rest during a long trip, it's recommended to find a safe and appropriate place such as a designated rest area, campground, or hotel. Additionally, always follow safety guidelines and recommendations provided by the vehicle manufacturer.