Sure, McDonald's may be getting all the press as an official Olympics sponsor, but sponsorship deals have been going on since 1908.
BBC has a fascinating audio slideshow about how sponsorships started. Turns out, the very first sponsor was Oxo, back at the 1908 London games. The soup stock company provided athletes with hot and cold beef stock drinks (which are a thing, we guess) and rice pudding.
Then, Coca-Cola signed on in 1928, starting with the Amsterdam games. When the Olympics hit Los Angeles in 1932, the Coca-Cola company hired 1,000 people to hand out Cokes while wearing white gloves. There's even a section on the controversial Germany games, where they outsourced their advertisements, and the following games where they handed out swag bags containing everything an Olympic-goer would need.
As for other sponsors? Now, McDonald's, VISA, and other sponsors have exclusive rights during the games, meaning a sponsorship is as much a cash cow as it is great advertising. Head on over to BBC to hear the complete story (and see some amazing vintage shots).