<li><label><input name="answer_{{ $loop->iteration }}" type="radio" value="a">Постоянно</label></li>
<li><label><input name="answer_{{ $loop->iteration }}" type="radio" value="b">Иногда</label></li>
<li><label><input name="answer_{{ $loop->iteration }}" type="radio" value="c">Время от времени</label></li>
var item = document.getElementsByClassName('b-sidebar__menu__item');
for (var i = item.length - 1; i >= 0; i--) {
item[i].onclick = function(){
this.classList.add('b-sidebar__menu__item--clicked');
}
}