1 1/2 cups cold raspberry lambic, such as Lindemans
Combine sugar and water in a small saucepan over medium heat, stir to mix, and bring to a boil. Reduce heat and simmer until sugar is completely dissolved, about 3 minutes. Remove from heat and let cool in the refrigerator until cold.
Place lambic and chilled simple syrup in an ice cream maker and freeze according to the manufacturer’s instructions. Transfer to an airtight container and chill in the freezer for at least 8 hours to set.