Buy Saint Archer Gold 6 or 12 pack in the store. Go to the offer page. Snap a photo of the sales receipt.
Wait a few days for notification. Full amount (up to $20) will be deposited in your PayPal account.
Edit: in some states, the rebate is only 50%.
Must be 21.
Works in 37 states.
Must have Paypal account.
Personally, I purchased a 12 pack (that's all the store carried), and I got back $15.99 in about a week.