Frequent renter benefit programs may offer rewards and benefits that include a free rental car with a certain number of rentals. You can look at Overview of Frequent Renter Program Benefits to find out details of various car rental company

If you own a small business or rent on business, many car rental business programs also offer free rental car coupons after a number of qualifying rentals. Check Business Car Rental Program Benefits for more details.

One other thing that you may want to look into is rental car coupons or certificates as part of any frequent flyer reward programs that you may have. Most frequent flyer programs allow you to earn airline miles with your car rental. They also usually offer programs where you can redeem accumulated reward miles or points for car rental reward certificates, including certificates for free days.