Dog food delivery and purchase options. One of the most common places where people buy dog food is in supermarkets such as Walmart. However, more and more dog owners are turning to the World Wide Web to find customized dog foods that meet their very own pets’ specific needs and niche brands of wet, dry, and grain-free dog foods to keep their pups in working order. Dog food is heavy, so if you can order it online, or set up a subscription for it, then it’s perfect.