Add hot chocolate mix and granulated sugar to large gallon sized pitcher. Pour in hot coffee, stirring to combine and make sure the hot chocolate mix and granulated sugar have dissolved. Pour into a punch bowl and add hot water. Stir to combine. Add scoops of chocolate ice cream and serve warm.
To serve cold: Mix hot chocolate mix, granulated sugar and coffee together until sugar has dissolved. Add water and refrigerate 4 hours to overnight. Add scoops of chocolate ice cream about 15 minutes before serving.