All berries are great sources of fiber. Fiber helps keep your digestive system healthy and is good for your heart. All berries are good for you so mix it up. Raspberries have the most fiber at 8 grams per cup, compared to the same number of blueberries which has half the fiber but is packed with antioxidants that may help keep memory sharp. A cup of strawberries contains 3 grams of fiber, but more than a full day's recommended dose of vitamin C.