There is no prize. It's just an annoying marketing thing.
People like to say "if you're not paying, you're the product." Except here, there was no benefit to the participants. So it doesn't even rise to that level — you're just being manipulated and taken advantage of by participating at all.
It would be funny if Sirius actually does spend time and effort on an "investigation." Then they won't get all of this quite totally for free.