Spinning 360 degrees, using Tween.Rotation is a bit unwieldy.

[octia]

Now, I might be wrong. But I think this is the easiest way to spin something 360 degrees, endlessly on loop.

Sequence s = Sequence.Create(-1, CycleMode.Restart, Ease.Linear);
s.Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -90f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -180f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -270f), rotationTime/4f))
    .Chain(Tween.Rotation(target.transform, new Vector3(0, 0, -360f), rotationTime/4f));

Ideally, a single Tween.Rotation could achieve it, but to my knowledge, it cannot. Am I wrong?

[KyryloKuzyk]

You are correct on the part that it's not possible to animate rotation beyond 180 degrees when using Quaternion (transform.rotation). But it is possible to create 360 rotation with the help of transfrom.eulerAngles property, like this:

// Rotate 'transform' around the z-axis by 360 degrees in 1 second 
Tween.EulerAngles(transform, startValue: Vector3.zero, endValue: new Vector3(0, 0, 360), duration: 1);

The only caveat of using Tween.EulerAngles() is that you should always specify the startValue to prevent inconsistent results. Please read more on this here: https://docs.unity3d.com/6000.0/Documentation/ScriptReference/Transform-eulerAngles.html