Can I make gravity work the other way round for one object?

Hi, I'm trying to make a game where you control a car (a 4 wheel colliders and 1 rigid body setup) and can switch gravity for that car alone.

I'm pretty new to unity and haven't got a clue where to start, I'm also completely useless at scripting (I'm more of a game artist). I thought maybe I could change the mass to a negative value, but unity won't allow it so that didn't work...

Anyway, any assistance at all would be greatly appreciated!

Sure, just turn that object's gravity off using .useGravity, eg:

rigidbody.useGravity = false;

Then apply your own equivalent gravity in the direction you want, either using AddForce in FixedUpdate, or by adding a ConstantForce component.

Here's a simple example using the "AddForce" method, which switches gravity when you hit spacea:

private var gravityReversed = false;

function FixedUpdate() {
    if (gravityReversed) {
        rigidbody.AddForce(Vector3.up * Physics.gravity.magnitude);
    } else {
        rigidbody.AddForce(-Vector3.up * Physics.gravity.magnitude);
    }
}

function Update() {
    if (Input.GetKeyDown(KeyCode.Space)) {
        gravityReversed = !gravityReversed;
    }
}