Spice up your smoothies and you'll never suffer through a boring apple-banana smoothie again! Think lemon zest, cranberries or pomegranate juice for a sour touch. For some extra zing, add a pinch of chili pepper or some freshly grated ginger. For some crunch you can add chia seeds, and for natural sweetness try honey or dates. And when it comes to spices, ground cardamom, cinnamon, nutmeg and cloves all add an extra layer of warmth to your smoothie.