Change your code this way
$(function () {
$('#<%= add_order.ClientID %>').on('click', function () {
var name = $('#<%= name1.ClientID %>').val();
var drink = $('#<%= drink1.ClientID %>').val();
var items="<li>name: " + name + ", drink: " + drink + "</li>";
$('.orders').append(items);
return false;
});
});
Regards..