In a shaker, pour 1 tbsp (15 ml) of cool water. The exact amount is key to making a fine foam - if you have less water, it will not work, while if it is too much, the foam will have a thin consistency.
Add the instant coffee and sugar to the water, and beat everything continuously. In a suitable glass, drop 2 ice cubes and pour the frappe in. Top up with milk to get a white frappe.