Spriter.cs

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


namespace HelpPeople
{
    [System.Serializable] public class Pair //simple mutable "POD-struct"
    {
        public Pair(SpriteRenderer sr, Transform t, float d) { spriteRenderer = sr; transform = t; distance = d;  }

        public SpriteRenderer spriteRenderer;
        public Transform transform;
        public float distance;
    }

    public class Spriter : MonoBehaviour
    {
        [SerializeField] private List<Pair> renderers;
        [SerializeField] private Camera cam;

        private void LateUpdate()
        {
            var camPos = cam.transform.position;
            for(int i = 0; i < renderers.Count; ++i) //just set distance to all before sort
            {
                Pair current = renderers[i];
                current.distance = (camPos - current.transform.position).sqrMagnitude;
            }

            renderers.Sort((r1, r2) => r1.distance.CompareTo(r2.distance));

            for(int i = 0; i < renderers.Count; ++i) //set order in simplest way, one by one
            {
                renderers[i].spriteRenderer.sortingOrder = i;
            }
        }
    }
}