Milan Steskal said
10 months ago: @haleysunshine, posting a coupon code into a status update should work. People may start to share it if the product is interesting.
Regarding building and managing an app, you don’t need to spend fortune to have someone build a custom fan gating coupon or sweepstakes promotion for your Facebook page. There are some tools, which let you do so for free or for very reasonable $$