Sometimes during development, you need to run the same post update hook repeatedly. Instead of resetting Drupals internal registry on already-run updates, we can also use drush to run a specific hook manually.
9.x
I couldn't find information on this easily, so I thought it's worth putting this here.
The equivalent of drupal_var_export() / ctools_var_export() in Drupal 8/9 is Variable::export():