Watermelon Lemonade Slushie

5 cups cubed, frozen seedless watermelon
1 lemon, juiced
Sugar or maple syrup, to taste but start with 1-2 tablespoons
Cold water

Add frozen watermelon cubes, lemon juice, and sugar or maple syrup to a blender. (A high speed blender works best here.) Add just enough water to make it blendable. Blend until it has a slushie consistency. Add more water if needed but not too much. You don’t want to lose the thick consistency. Makes about 2 servings.