You could add fake reviews but Im not sure if having reviews already will make people want to add their review. Perhaps you could think about why reviews are not being added by your customers/users and try and make the process of adding reviews better.
I send an email to customers after they have made a purchase inviting them to add a review and explaining that their review will help others by offering a customer perspective on that product.
I'd look at the process of adding a review on your site is it obvious how to add a review? how does it compare to other sites? and is it an easy and quick process? The less effort required to add a review the better, IMO.