In the bottom of a blender, add water, banana, protein powder or Greek yogurt, and vanilla extract. Blend until smooth.
Notes
Bananas: Use fully-ripe or slightly overripe bananas (brown spots mean naturally sweet!). See Recipe FAQs for tips on how to ripen bananas in your oven. Bananas can then be peeled and frozen (for the best texture in your smoothie, frozen bananas are a must!).
Protein powder: Use either your favorite vanilla protein powder or ½ cup Greek yogurt.
Yield: This recipe makes about 2 cups of smoothie, enough for 1 serving.
Storage: Store leftovers covered in the refrigerator for up to 4 days. Some separation may occur, so shake or stir to combine before enjoying.