I like watermelon and strawberries. A bit of lemon, or cantaloupe, or cinnamon creates a significant flavor change.

To extend the mixture I use honeycrisp apple cider or ginger ale and add 3 ice cubes. Plain water is even better for purists.

When blending oranges, I cut off the narrow internal orange slice fiber. Adding blueberries ruins the color but tastes good.
ALL these are rich in antioxidants and bioflavonoids.