How to make Bouncy Ball with 200% Efficent?

You can do this manually:

 using UnityEngine;
 
 [RequireComponent(typeof(Rigidbody))]
 public class TestScript2 : MonoBehaviour
 {
     [SerializeField] private float forceMultiplier;
 
     private Rigidbody rb;
 
     // Start is called before the first frame update
     void Start()
     {
         rb = GetComponent<Rigidbody>();
     }
 
     private void OnCollisionEnter(Collision collision)
     {
         Vector3 contactNormal = collision.GetContact(0).normal;
         Vector3 relativeVelocity = collision.relativeVelocity;
         float magnitude = relativeVelocity.magnitude;
         float force = Mathf.Sqrt(forceMultiplier * magnitude * magnitude);
 
         Vector3 velocity = Vector3.Reflect(-relativeVelocity.normalized * force, contactNormal);
 
         // Use this if you want to change the velocity, instead of bounce height:
         // Vector3 velocity = Vector3.Reflect(-relativeVelocity * forceMultiplier, contactNormal);
 
         rb.AddForce(velocity, ForceMode.VelocityChange);
     }
 }