You can get one of these bottle caps from mailing in barcodes.
There's also a lottery for a plate and a plush. (artist mockups)
Unfortunately there are about a 1000 of each.
While I doubt I can get a plush, I'm definitely going to try to make the omlet rice featured on the campaign page (Japanese). English article on the promo.
For those that are entering, good luck, and enjoy your ketchup!