Getting back to the point of your original post: the best option for renting in Berlin. Quite simply, it's just a matter of getting on the car rental websites and doing your homework. No one on this Forum can answer your question, as asked, because only you know what kind of car, dates, car size, price you're willing to pay, etc. Also, things are constantly changing at those websites, so no one can tell you anything with any degree of certainty.