They do actually get the product for free. But they have to pay for the cups (which I did not know about Disney but knew about movie theaters--it's why when you ask for an extra cup they won't give you one, because they are so strictly inventoried). This is apparently a common practice among soda dealers who want to eliminate competition in a given market (like a theme park), and want to require their logos be on the product when it goes out.
http://disneylies.com/legends/disneyland.html
"Legend: Because of the advertising value of having its products featured at Disney theme parks, Coca Cola provides
Disneyland with all of its beverage products free of charge.
Behind the Legend: This is true, but highly misleading. For years, Coke has had an advantage over rival Pepsi because it provides its products free of charge to all of its customers. The company makes up the loss by requiring that beverages only be sold in official cups or containers -- and charging an enormous amount for those contains. The container charge is based on a sliding scale depending on the customer. Individual consumers, purchasing beverages at a grocery or convenience store, pay only a few cents for the can or bottle in which their beverage comes. At the other end of the scale, movie theaters and theme parks like Disneyland pay as much as $2.00 for a single drink cup, making the exorbitant prices charged for drinks at those locations completely understandable."
I wasn't not sharing links because they were untruths, but because it confounds me when people, who are sitting in front of a computer as they are typing, try to derail conversations or ideas by insisting on being handed proof on a platter. You have Google. Use it. If you find conflicting information, then join the conversation with some useful data to further the discussion. I made my statement based on my research, and I am not here to do your research for someone else. That said, if someone asks politely for further information in the spirit of genuine curiosity, I am happy to share resources and forward the overall discussion. That was clearly not the case.
Edited to add: oh and the reason why I knew about the markup on wines is because I worked in restaurants for 8 years--it was firsthand, real world experience. I didn't read it on a web page to learn that, so there was no "link" I had to share.