Pour 1 tablespoon of the brewed espresso into a large measuring cup or bowl. Whisk in the sugar until the sugar is dissolved and the espresso resembles a paste. Top with the remaining espresso. Fill 2 glasses with ice and divide the espresso between the glasses. Add the milk and more ice to a quart jar and shake until the milk is very cold and frothy. Top each glass of espresso with half of the milk. Stir and serve immediately.