In a large saucepan, combine sugar, water, and jell-o. Boil for 3 minutes. Stir in pineapple juice, lemon juice, and orange juice. Divide mixture into two separate containers (I use gallon-sized Ziploc bags) and freeze for at least 8 hours (it can store in the freezer for a long time, but if you want the "slushy" consistency, you will want to keep it in the freezer for at least 8 hours).
If it is frozen solid, I usually pull it out of the freezer about 2 hours before I need to use it so that it can thaw a little bit.
When ready to serve, place the slushy contents of the bag into a punch bowl and stir in a 2 liter of Sprite with it (if you need to serve a lot of people, you can add a second 2-liter of Sprite and it will still taste good). I like to slice up some fresh strawberries and throw them into the punch bowl.
Serve immediately.
Notes
If you do not like orange juice, you can swap it out for another juice such as grapefruit juice, passionfruit juice, pineapple juice, mango juice, or lemonade.This recipe is made for drinking. However, if you want to preserve the recipe, you can make it into popsicles. The popsicles will loose a bit of carbonation, but the lemon-lime and strawberry flavor still comes through effectively. If you do not have popsicle molds, use plastic cups with the wax lining. They are easier to cut off and do not stick when frozen.