This was served at a little sandwich shop that was located in the office building where I used to work. During the summer I make this several times a week - it's so delicious and refreshing! I like it with red grapes, but green will work as well!
Cut the watermelon into small cubes, or make balls using a melon baller.
Slice the strawberries.
Cut each of the grapes in half.
Mix all fruits in a bowl.
Stir the sugar and cinnamon into the orange juice until both are dissolved. Placing in a jar and shaking works well for this too (the amount of sugar and cinnamon may be adjusted to your personal taste).
Pour the juice over the fruit and stir until well coated. You may not use all of the juice mixture, but don't use too little - make sure all of the fruit is well coated.