There are very simple but filling cooked meals available at Chiquisca, Santa Rosa and Marampata. A plate of food or bowl of soup will cost you about 3 soles. These locations also sell soft drinks, snacks, and the ubiquitous.
A local entrepreneur has wisely opened a shop with Gatorade and snacks about 10 minutes before you find another shop. Apologize to the nice lady for having already bought your snacks at the first store. Just past a gate is the top and you are rewarded with the first views of the Incan site and a nice bench to eat lunch at. Hike another hour or so and stake out your campsite. Explore the lower site that day and then see the rest of the sites on the following day. Unless you are in great shape, the relaxing day of exploring the site is necessary and must be done to truly enjoy the site. In every camp site along the way locals have set up shop, so you can buy water, soda, rice, snacks, eggs and fruit.