I want to destroy a child object when player collides with the parent object

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class FruitGrowth : MonoBehaviour
{
    //ParentObject is "Bloom", and the child object under it is "Fruit"
    public int RegrowRate = 5;
    private int timer = 0;

    void update()
    {
         //fruit = false (collided/Eaten), then timer start, and if time = regrow rate, fruit = true (regrow)
    }

    public void OnColliOnCollisionEnter2D(Collision2D collision)
    {
        if (collision.gameObject.name == "Sprite")
        {
            //then destroy Fruit

            Debug.Log(collision.gameObject.name);
        }

    }
}

So you need to put a script on the object with the collider e.g.:

public class Bloom : MonoBehaviour
{
   // here we assign the object that we want to destroy via editor
   public GameObject Fruit;

   // then you have some custom method for destroy where you destroy your child object
   public void DestroyFruit()
   {
      Destroy(Fruit);
   }
}

Then you modify your OnColliOnCollisionEnter2D method like this:

public void OnColliOnCollisionEnter2D(Collision2D collision)
{
        Bloom bloom = collision.gameObject.GetComponent<Bloom>();
        
        // if collision with the object with Bloom script on it
        if (bloom != null)
        {
            //then destroy Fruit
            bloom.DestroyFruit();
            Debug.Log(collision.gameObject.name);
        }
}

got it Thanks man