You should use code similar to the following one.
public function myPage() {
\Drupal::service('page_cache_kill_switch')->trigger();
return [
'#markup' => time(),
];
}
Recently, Add #cache[max-age] to disable caching and bubble the max-age was committed.
When $build['#cache']['max-age'] is not set, permanent cache is assumed. To indicate that a render array should not be cached at all, set $build['#cache']['max-age'] to 0 (i.e. 0 seconds); to indicate that a render array should be cached only for a limited period, e.g. 5 minutes, set $build['#cache']['max-age'] to 300 (i.e. 5 * 60 seconds).
After, clear the cache.
