In the list of foods that contain high amounts of potassium, sweet potatoes ranked the highest. One large sweet potato can provide 855mg of potassium and 101 calories. It also contains fibers, beta carotene, carbohydrates, vitamin C, and vitamin B6. Research has even shown that sweet potatoes display anti-ulcer activity. They can be eaten stuffed, mashed, baked, grilled, or fried. Sweet potatoes are one of the healthiest foods.