Are those hackathons sponsored by one of the largest corporations in the world, one that is asking you to revolutionize a product for pennies on the dollar?
It is essentially a corporate takeover of the hackathon without understanding of it at all. Most sponsored hackathons are, "Hey write for our API, here is food and $2K and some t-shirts."
Coca-cola is just hitching on the whole notion of the hackathon, hoping someone is willing to work for cheap on something that can probably bring them a billion if it all works out.
Edit: I should probably note that its their event and they have the right to set the prizes, but man, $10K is low for something that can earn Coca-cola a lot of money.