Add the watermelon, strawberries, banana, and almond milk to a high-speed blender. Blend until very smooth.
Taste the smoothie, and add the maple syrup if it needs extra sweetness. (You can also use half of a pitted Medjool date instead.) Blend again, and then serve immediately for the best flavor and texture.
Nutrition information is for the whole batch. This information is automatically calculated and is just an estimate, not a guarantee. Looking for a more slushy texture? Add a handful of ice or frozen watermelon cubes to create a thicker texture.