I started with a half gallon of Guava Mango juice, a half gallon of lemonade (Tropicana now makes a line called Trop50 which contains 50% less sugar), and some fresh fruit. I used 1 grapefruit, 3 oranges, and 3 lemons, but you could use whatever you like and have on-hand!
Pour the store bought juices into a pitcher. (I dilute the juice with a little water at the end, so I end up with more than a gallon. Therefore, I divide the juice evenly into 2 containers.) Next, squeeze the juice from the fresh fruit into the pitcher. If you have a small strainer, you may want to use that to get out any seeds or large pieces of pulp that found their way into the juice.
Finally, add water to dilute to desired to taste and agave syrup (or sugar), if needed, to desired taste. I add about 1/3 of a pitcher of water to each gallon of fruit juice. I find straight fruit juice from the store to be too heavy and concentrated. This drink is much more light and refreshing!! And although I wouldn't call this a completely healthy drink, it's definitely a healthier alternative to drinking straight sugar-filled fruit juice from the store!