Event Espresso 4 Attendee shortcode custom loop, sorted by answer to custom question. You add this to your child theme.

loop-espresso_event_attendees.php

<?php
/**
 * Loop Template for the [ESPRESSO_EVENT_ATTENDEES] shortcode
 *
 */
$no_attendees_message = apply_filters('FHEE__loop-espresso_attendees-shortcode__template__no_attendees_message', __('No Attendees Yet', 'event_espresso'));
?>

<div class="event-attendees">
	<?php
do_action('AHEE__loop-espresso_event_attendees__before', $contacts, $event, $datetime, $ticket, $show_gravatar);

if ($contacts): ?>
		<ul class="event-attendees-list">
<?php
    $attendee_list = array();
    foreach($contacts as $contact):
        $custom_question_output = '';
        if ($contact instanceof EE_Attendee) {
            $prev_answer_value = EEM_Answer::instance()->get_var(array(
                array(
                    'Registration.ATT_ID' => $contact->ID(),
                    'Registration.EVT_ID' => $event->ID(),
                    'QST_ID' => 11 // replace with custom question's ID
                ),
            ), 'ANS_value');
            if ($prev_answer_value) {
                $custom_question_output = $prev_answer_value . ' - ';
            }
        }
    $attendee_list[] = $custom_question_output . $contact->lname() . ' ' . $contact->fname();
    endforeach;
    sort($attendee_list);
    foreach($attendee_list as $attendee) {
        echo '<li>' . $attendee . '</li>';
    }
?>
		</ul>
	<?php
else: ?>
		<p><?php
    echo $no_attendees_message; ?></p>
	<?php
endif; ?>
	<?php
do_action('AHEE__loop-espresso_event_attendees__after', $contacts, $event, $datetime, $ticket, $show_gravatar); ?>
</div>