JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

  <body>
    <div class="btn-group" data-toggle="buttons">
      <span id=car></span>
    </div>
  </body>

</html>

CSS

.radio-toolbar input[type="radio"] {
  display: none;
}

.radio-toolbar label {
  display: inline-block;
  background-color: #ddd;
  padding: 4px 11px;
  font-family: Arial;
  font-size: 16px;
  cursor: pointer;
}

.radio-toolbar .radio {     /* style the wrapper */
    position: relative;     /* allows to "hide" the radio (won't occupy space) */
    display: inline-block;  /* show wrappers in horizontal line */
}

.radio-toolbar input[type="radio"] { /* hide the <input> */
    position: absolute;
    z-index: -1;
}

.radio-toolbar input[type="radio"]:checked + label { /* target the <label> */
  background-color: #000;                            /* changed to more obvious color */
}

JavaScript

var array = ["Saab", "Volvo", "BMW"];
var item = document.createElement('div');
item.className = 'radio-toolbar';

for (var i = 0; i < array.length; i++) {

  var wrapper = document.createElement('div'); // <-- create a wrapper element
  var input = document.createElement('input');
  var input_label = document.createElement('label');

  input.type = 'radio';
  input.name = 'radio-btn';
  input.id = 'radio' + i;
  input.checked = i === 0;
  input.value = array[i]; // <-- <input>s should have different values
  
  input_label.htmlFor = 'radio' + i; // <-- connect label to <radio> via for-attribute
  input_label.innerHTML = array[i];
  input_label.className = "btn btn-primary";
  input_label.appendChild(input);
  
  wrapper.className = 'radio'; 		// <-- add a class to the wrapper
  wrapper.appendChild(input);  		// <-- add the <input>
  wrapper.appendChild(input_label); // <-- add the <label>


  item.appendChild(wrapper);		// <-- add wrapper to toolbar
  document.getElementById("car").appendChild(item);
}