JSFiddle - React, Tailwind, and code Playground

HTML

<div class="group origin">
    <label><input type="checkbox" name="UPDATE_METHOD[0][]" value="Email" checked="">Email</label>
        <label><input type="checkbox" name="UPDATE_METHOD[0][]" value="SMS" checked="">SMS</label>
</div>
      
      <a href="#" class="cloner">Clone!</a>

JavaScript

var original= $(".origin");
var cloneNum = 0;
$(".cloner").on("click", function(e){
    e.preventDefault();
    
    cloneChecks();
});

function cloneChecks(){
    console.log("cloning..."); 
    cloneNum++;
    var clone = original.clone();
    clone.removeClass("origin");
    clone.find("input").each(function(){
        $(this).attr("name", "UPDATE_METHOD[" + cloneNum + "][]");
    });
    original.after(clone);
}