Hi @rudtek
I’m afraid ACF doesn’t handle a pretty permalink like that. I believe you need to modify your .htaccess file to do that. For further support, WordPress support forum would be the best place to get it.
If you don’t need pretty permalink, you can always use a parameter like this:
http://www.mysite.com/events/my-event/?sponsors=sponsors+name
This page should give you more idea about it: https://www.advancedcustomfields.com/resources/creating-wp-archive-custom-field-filter/.
I hope this helps 🙂