In a medium bowl, combine instant coffee, granulated sugar, and hot water.
Whisk vigorously or beat with a hand mixer on medium-high until the mixture is very thick, glossy, and holds medium-stiff peaks, 3–5 minutes with a mixer or 8–12 minutes by hand.
Divide ice cubes between two 12-ounce glasses and pour whole milk into each.
Spoon the whipped coffee evenly over the milk. Serve with a spoon or straw and stir to taste.