You can substitute almond or oat milk for dairy milk to make it dairy-free, or use another nut butter like almond or sunflower seed butter if peanut allergies are a concern. For a sweeter drink, use ripe frozen bananas or add more honey. Prep smoothie mix in advance and keep it in the fridge for up to one day, shaking before serving. If the smoothie separates, blend again before drinking. If your mixture is too thick, add a splash more milk; if too thin, add a few ice cubes or extra banana slices and re-blend until desired consistency is reached. Avoid using hot coffee to prevent curdling of milk.