1. Juice lemons. Save halves for serving.
2. In a small saucepan over medium heat, combine water, sugar, and lemon zest. Stir well. Bring to a boil, then reduce heat to low and simmer 3 minutes. Remove from heat and allow to cool.
3. Strain cooled water, sugar, and lemon zest mixture into bowl.
4. Stir in 2 cups of freshly squeezed lemon juice and 1/2 cup of lemon-lime soda.
5. Transfer to a 9 x 13 metal baking pan. Place in freezer (for 2-4 hours). Stir with fork every half hour.
6. Scoop into lemon half, garnish with mint.