I would say that the products (food and drink) are being used to promote the game.
Explaining my thought process behind this is actually quite easy as you're the perfect example for it. Even though you did not buy the packet of crisps or the can of Monster, you still noticed the game that was being advertised, and that's what the goal of the game publishers will be.
These particular food stuffs are sold all around the country, that is a huge reach. Every time someone walks into a store, be it your local corner shop or a larger super market that person is likely to see the product and so the game label. But unlike the actual can of drink or what-have-you, it doesn't matter if you buy it or not. If you look on the product, notice the game name, you'll think of the game and thus the chances of you buying it (or playing it more if you already have it) increases, even if it is just a tiny bit.
The tl;dr version:
These game companies are using the food stuffs as a huge advertising campaign that reaches around the country. All you need to do is notice them and the campaign is doing it's job.
If this was a competition dude your comment would win. A quality ezpla