try ADAC (the German AAA - https://autovermietung.adac.de/mietwagen/). Member rates are better than non-member rates, but they all tend to come with "no excess", "unlimited mileage", and "extra drivers included" options. They partner with Sixt, Hertz and Avis among others, and I always got competitive quotes from them.

You might even benefit from joining ADAC as a "Basic" member, whch is available for foreign residents and costs € 54 per year. That will be enough get you the "member" price and conditions (https://www.adac.de/mitgliedschaft/).