This is only possible because Aru is an outlaw.
In real life, sticking your upper body out of a moving car is extremely dangerous, so DO NOT try this.

A relative of mine knew someone who did this in college. Don't know the details, just that the car that guy was in ended rolling over while he was doing it and my relative had to attend his funeral.

Though if what others have told me about Aru is true, she’s probably gonna regret this in about 30 seconds.

The car is actually still, and it's someone blowing a fan at her. Welcome to life.