Bring the sugar, water, and Jell-O to a boil in a large stockpot.
Boil for 3 minutes.
Mix in the pineapple juice, lemon juice, and orange juice.
Divide mixture into 2 gallon ziplock bags and freeze by laying bags flat in a baking pan.
Combine the contents of 1 ziplock bag with 2 bottles of the lemon-lime soda in a punch bowl.
Stir until it reaches a slush-consistency.
Repeat steps 5 and 6 with the second bag.
Notes
Balancing Sweetness: Adjust the amount of sugar to suit your taste preferences. While the recipe calls for 1 ½ cups of white sugar, you can reduce or increase the amount based on how sweet you want your slush punch to be. Keep in mind that the sweetness of the Jell-O mixes and fruit juices will also contribute to the overall flavor, so tasting the mixture before freezing can help you gauge the sweetness level.
Freezing Technique: When freezing the punch mixture in ziplock bags, ensure they are sealed tightly and laid flat in a baking pan. This allows the mixture to freeze evenly and prevents spills or leaks in the freezer. Make sure the bags are fully frozen before proceeding to the next step. Overnight freezing is recommended to achieve a solid slush consistency.
Punch Assembly: When ready to serve, combine the frozen punch mixture with lemon-lime soda in a punch bowl. Adding the soda gradually while stirring helps to achieve the desired slush consistency. Be gentle when stirring to avoid breaking up the slush too much. Consider keeping extra soda on hand to adjust the consistency if needed, as the amount may vary depending on personal preference and the level of slushiness desired.