I have tried many things but none works except of this 🙂
global $wpdb;
$qry = "SELECT post_excerpt as 'field_name', post_name as 'field_key' FROM <code>wp_posts</code> where post_type = 'acf-field'";
$results = $wpdb->get_results( $qry, ARRAY_A );
Wrap it in a function in the functions.php file.
Hope this works