Markup
<div class="sb-form-control">
  <label class="sb-label" for="dropdown-id-search-no-results">Select options</label>
  <div class="sb-dropdown sb-dropdown--open" id="dropdown-id-search-no-results">
    <div class="sb-dropdown__button sb-form-control__input sb-form-control__input--icon-right">
      <button class="sb-input" aria-label="Select options">
       Select options
      </button>
      <svg class="sb-icon" viewBox="-5 -5 16 16"><path d="M0 0l3.5 4L7 0H0"></svg>
    </div>
    <ul class="sb-dropdown__menu" role="listbox">
      <li class="sb-dropdown__search" role="search">
        <input class="sb-input" id="input-id-2" placeholder="Search here ..." aria-label="Search">
      </li>
      <li class="sb-dropdown__message" tabindex="0" aria-label="No results">
        No results
      </li>
    </ul>
  </div>
</div>
Source: components/_dropdown.scss, line 266