A function that allows you to clear all transients either by running the function, calling it via AJAX, or by calling it via CURL

wp_hm_clear_transients.php

<?php
// Clears all transients, can be ran via the function, via AJAX or by manually running:
// curl -d "action=hm_clear_transients" https://website.com/wordpress/wp-admin/admin-ajax.php
add_action('wp_ajax_hm_clear_transients', 'hm_clear_transients');
add_action('wp_ajax_nopriv_hm_clear_transients', 'hm_clear_transients');
function hm_clear_transients() {
  global $wpdb;
  $rows = $wpdb->query("DELETE FROM $wpdb->options WHERE option_name LIKE '%_transient_%'");
  if (wp_doing_ajax()) wp_send_json_success($rows);
  return $rows;
}
?>