Imagine a Custom Post Type of "Fruits" that would normally display as: mydomain.com/fruit/TITLE
Is there any way to change this to give something like: mydomain.com/fruit/POSTAUTHOR-TITLE/ or mydomain.com/fruit/CONNECTEDPOSTVIARELATIONSHIP-TITLE/ ?
Unfortunately not this isn't possible unless some custom coding is used. The rewrite exists so that you can change the default slug to any that you choose.
Not sure why you would need this either. However you can add the author in the slug with the wordpress default permalink settings but it will be applied for every post.