So my box of Poptarts came with a code for a Poptarts promotion (poptartsflavorcard.com). Up for grabs for anyone who wants it since I rarely eat Poptarts so I have no need for the code
According to the Poptarts box, there's some promotion running on Poptartsflavorcard.com where submitting a certain number of codes gets you prizes. So I guess it's similar to My Coke Rewards.