Combine 2 tablespoons of water, instant coffee, and sugar in a medium bowl. Using a large whisk or a hand blender, whisk until the mixture is light in color and holds a firm peak, 3 to 4 minutes. Put a few ice cubes in a tall glass, then add the milk. Dollop coffee mixture over the milk to fill the glass. For best results, stir with a tall spoon or reusable straw.