Those V-8 Splash juices supposedly have a serving of vegetables too, but I think they either have a lot of sugar or salt as well. Have you tried baking sweet potato fries? Look around for recipes, most call for a light coating in an oil, salt, pepper, (sometimes brown sugar) mixture.
*erm, scratch the v-8 splash juices, they're made with evil high fructose corn syrup. Their v8 Fusion line at least has 100% juice, no HFCS. But I'd still pay attention to the sugar content on the label.