Multisite Cache Clear I have a site with multisite settings

There is one main site, where all the news are created and those are gotten by the other sites via a direct db_query via a taxonomy tid. This is the part that I managed to work after all.

Now the problem.
When I create or update a news node on the main site, the others have to be somehow notified of this. But I don't know how I can clear the cache of a different site


Is there some module which can do this?
If not, do I have to delete from cache tables directly on hook_node_update(), hook_node_delete(), hook_node_insert() ?
If yes, which table(s) does drupal store the cached rendered output (or doesn't she?)?
…  
I cannot use drush
One thing might help you(not sure)is that you can write your function in hook_cron and run that cron in background. So let's say your cron run after every 5 min, which means your page is refreshed and cache will get clear on every cron hit.