float ClampAngle(float angle, float from, float to)
 {

     if (angle < 0f) angle = 360 + angle;
     if (angle > 180f) return Mathf.Max(angle, 360+from);
     return Mathf.Min(angle, to);
 }


void FixedUpdate(){
    //...
    var clampRotation = can.transform.rotation.eulerAngles;

    clampRotation = Quaternion.Euler(rotation.x, rotation.y, ClampAngle(rotation.z, -45, 45))
    can.transform.rotation = clampRotation ;
    ///..
}