Chill a mixing bowl and whisk
Pour 2 cups cold fruit juice or fruit puree into the bowl
Add 1 cup sugar
Add 1 cup milk or half-and-half
Add 1 tablespoon lemon juice
Add 1 teaspoon vanilla extract
Whisk until the sugar dissolves
Taste and adjust sweetness if needed
Pour the mixture into an ice cream maker
Churn according to the machine instructions
Transfer to a freezer-safe container
Freeze until firm
Scoop and serve