Pour water into 2 quart microwave safe casserole. Microwave at high setting 1 minute, then stir in instant coffee granules until dissolved. Blend in sugar and cinnamon then pour in milk, stirring constantly. Microwave, uncovered, at medium setting 5-9 minutes, stirring every 3 minutes, or until heated through. Serve in mugs topped with a dollop of whipped cream and a sprinkling of nutmeg.