If you don't have a high-powered blender, you can still make this smoothie, but keep in mind that it won't be as smooth. It will still taste delicious!
If you're unsure about how a green breakfast smoothie will taste, opt for spinach as it's less green-tasting.
Make sure that at least one of the ingredients is frozen. We normally keep a bag of peeled bananas in the freezer for smoothies. If all of your ingredients are fresh, you can add some ice cubes to chill the smoothie.
The exact amount of water you need will depend on the size of the banana and apple you use, how many ingredients are frozen, and personal preference. It is best to start with 1 cup and then add more as needed.