Flush cache in case of WSOD without Drush on shared host
I get used to using Drush, especially when Drupal 8 website
  encountered an unexpected error, without this option I don't see the
  way how to clear the cache without UI.


Run www.mysite.com/update.php. This clears the cache, even when no updates are to run.

If you don't have access set $settings['update_free_access'] = TRUE; temporarily in settings.php.