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
This is the perfect drink for barbecues, baby showers, wedding showers, parties, Mother’s Day, or just on a hot summer day.