Grow some sweet potatoes in a large flower pot. Seems you can grow quite a few pounds in a plain under 10 dollar pot with holes in the bottom. You may need a drip line to keep it watered. 
David Ramsey shows how he grew sweet potatoes in a flower pot as he goes about harvesting them. He got a really decent harvest, they were growing so well he had potatoes growing out the holes in the bottom of the pot even.
He says “Think you don’t have enough room for sweet potatoes? See how many you can grow in big plastic tub. See the results! This tub had Jewels, one of our favorites. These will be great all winter. Easy to do, doesn’t cost much and great organic food for your family. ”
