Place the instant coffee in a jug, add the boiling water and stir until dissolved. Add the ProZero and the caster sugar and leave to cool.
Pour into a glass filled with ice and serve.
To make your coffee stronger, add more instant coffee.
ProZero is a food for special medical purposes and must be used under medical supervision. This recipe has been specifically designed for a low protein diet. Refer to labels for allergen and other product information.