$sponsor_link_url = get_post_meta( get_the_ID(),'sponsor_link_url',true);
  $sponsor_link_txt = get_post_meta( get_the_ID(),'sponsor_link_txt',true);

  $sponsor_link = "<a class=\"sponsor_link\" href=\"$sponsor_link_url\">$sponsor_link_txt</a>";

  echo $sponsor_link;