Gradually add sugar and vinegar until thick and glossy.
Place the coffee and water in a small bowl and stir till coffee is dissolved. Gently fold into egg whites. Use a 1/2 inch piping nozzle on to a tray covered with parchment paper, or just spoon. If you don't have a proper nozzle, just put into a ziploc sandwich baggie and cut a half inch hole into a corner.
Cook for 10 to 15 minutes until crisp on the outside. Turn off oven and let them cool completely.