Trigger a drush @sites cr --yes daily Drupal 8. 

Title sums up pretty much my question.

I'm wondering what is the best way to rebuild all my site's cache daily.

A cron job with Truncate table cache ?
Module who rebuild cache on each site ?

Does a plugin exist?
The simplest way is a cron job that calls drush @alias cr set for 24 hours. You can do that at the server level.