Here's the crucial paragraph:
As part of the, deal the company’s flagship premium beer, Heineken will be the branded lager served at the Games and Heineken UK will have exclusive pouring rights for its portfolio of beer and cider brands at all London 2012 venues where alcohol is served.
We do love going out for a portfolio or two on a Friday night.
So, that means you don't get any beer or cider on the Olympic Park unless its a Heineken booze drink. As all media accounts are sure to point out, the brand has finally achieved a literal truth with its slogan 'reaches the parts other other beers can't reach'.
This does raise an interesting point, which also applies to other official sponsors. What would happen if somebody showed up to the Games wearing, say, a football shirt with a rival beverage's logo emblazoned across it (Everton with their current 'Chang' shirt, for example). Would they be refused entry?
Image by Jason Webber in the Londonist Flickr pool.