Thankful they were able to rent me a car in such short notice after a reservation with a smaller company fell through after we landed. They were able to get me a car which was great but they never asked me anything if I wanted insurance, pre-paid fuel, etc. They just added it into the final fee and I asked was there any way to make the rate cheaper and she said no. So I said fine, let's do it. I get the bill and sure enough every since option was added - interior coverage, roadside assistance, third-party insurance coverage, pre-paid fuel. This cost me over 150 EUROS in unnecessary fees. Had they been more transparent, it would have been fine, but they added that in and didn't even communicate this to us. Unprofessional beyond belief and we were absolutely duped as a vulnerable renter.
UPDATE: Sixt Customer Service stepped in and offered a refund of a portion of the add-ons. Usually companies don't do this after the fact so I increased my rating to 4 stars. I am going to say this one a one-off and not indicative of the company practices.