How to Make It
Cook granulated sugar and water in a small saucepan over medium-high, stirring constantly, until sugar dissolves, about 2 minutes. Remove from heat; stir in evaporated milk and vanilla. Transfer to a heatproof bowl; let cool to room temperature, about 15 minutes. Refrigerate until cold, about 1 hour.
Place corn syrup in a rimmed small saucer. Place sanding sugar in a separate rimmed small saucer.
Dip glass rim in syrup, then dip in sanding sugar to coat. Repeat process with remaining 17 glasses.
Gently stir together chilled evaporated milk mixture, chilled soft drink, and desired amount of food coloring (start with 5 drops) in a punch bowl. Scoop ice cream into prepared punch glasses; ladle punch into glasses. Serve immediately.