Doha Rent a car is the cheapest.

Honda Jazz Qr.60/- per day.
Mitsubishi lancer / Civic Qr.70/- per day.
Honda Civic Qr.90/- per day.

But i guess should be atleast rented for a minimum of 4 to 5 days. During eid its very difficult to find rent car , need to book in advance.