How to add drift to top down car mechanics?

I'd like to add a sliding drift mechanic when spacebar is held. The code is for a 2d top down racing game. If there is already an answer for a question like this please direct me to it. Here is my pre-existing code:

 using UnityEngine;
 using System.Collections;
 
 public class Car : MonoBehaviour {
 
 public float power = 3;
      public float maxspeed = 5;
      public float turnpower = 2;
      public float friction = 3;
      public Vector2 curspeed ;
      Rigidbody2D rigidbody2D;
  
      // Use this for initialization
      void Start () {
          rigidbody2D = GetComponent<Rigidbody2D>();
      }
      
  
      void FixedUpdate()
      {
          curspeed = new Vector2(rigidbody2D.velocity.x,    rigidbody2D.velocity.y);
  
          if (curspeed.magnitude > maxspeed)
          {
              curspeed = curspeed.normalized;
              curspeed *= maxspeed;
          }
  
          if (Input.GetKey(KeyCode.W))
          {
              rigidbody2D.AddForce(transform.up * power);
               rigidbody2D.drag = friction;
          }
          else if (Input.GetKey(KeyCode.S))
          {
              rigidbody2D.AddForce(-(transform.up) * (power/2));
              rigidbody2D.drag = friction;
          }
           if (Input.GetKey(KeyCode.A))
          {
              transform.Rotate(Vector3.forward * -turnpower);
          }
          else if (Input.GetKey(KeyCode.D))
          {
              transform.Rotate(Vector3.forward * turnpower);
          }
  
          noGas();
  
      }
  
      void noGas()
      {
          bool gas;
          if(Input.GetKey(KeyCode.W) || Input.GetKey(KeyCode.S))
          {
              gas = true;
          }
          else
          {
              gas = false;
          }
  
          if (!gas)
          {
              rigidbody2D.drag = friction * 2;
          }
      }
 }