[WordPress] Add ACF Admin Column to Custom Post Type (In this example, CPT name = events & ACF column name = event_date). This also make the column sortable.

template-functions.php (for CPT)

// Add ACF Columns
function add_new_events_column($columns) {
    $columns['event_date'] = 'Event Date';

    return $columns;
}
add_filter('manage_events_posts_columns', 'add_new_events_column');

function add_new_events_admin_column_show_value( $column, $post_id ) {
    if ($column == 'event_date') {
		$evdate = get_field('event_date');
		echo $evdate;
	}
}
add_filter('manage_events_posts_custom_column', 'add_new_events_admin_column_show_value', 10, 2);

/* Make the column sortable */
function set_custom_events_sortable_columns( $columns ) {
  $columns['event_date'] = 'event_date';

  return $columns;
}
add_filter( 'manage_edit-events_sortable_columns', 'set_custom_events_sortable_columns' );

function events_custom_orderby( $query ) {
  if ( ! is_admin() )
    return;

  $orderby = $query->get('orderby');

  if ( 'event_date' == $orderby ) {
    $query->set( 'meta_key', 'event_date' );
    $query->set( 'orderby', 'meta_value' );
  }
}
add_action( 'pre_get_posts', 'events_custom_orderby' );