Rotate rigidbody2D towards target

I have A lot of gameobjects on scene I need to rotate. They are AI spaceships.
However this:

        Vector3 targetVector = targetPosition - myTransform.position;
        float angle = Mathf.Atan2(targetVector.y, targetVector.x) * Mathf.Rad2Deg;
        Quaternion q = Quaternion.AngleAxis(angle, Vector3.forward);

        myTransform.rotation = Quaternion.Lerp(myTransform.rotation, q, 5.0f);

Is soo performance HEAVY that there is no way I can use it. Is there some better way to rotate sprite towards target? (Mathf.Atan2 and Mathf.Rad2Deg are taking like 30fps with 1000+ objects)

From my answer to this question. You should use Quaternion.FromToRotation. And after that, use Quaternion.Lerp. Something like this (This code should be in FixedUpdate for smooth results):

Quaternion toRotation = Quaternion.FromToRotation(transform.up, targetVector);
transform.rotation = Quaternion.Lerp(transform.rotation, toRotation, 5f);

BTW in your code using Lerp makes no difference since you have passed t as 5 which is clamped to 1 which returns q directly.