Mix 2 teaspoons instant coffee with 2 tablespoons hot water. Stir until dissolved, then mix with 4 cups eggnog, 2 tablespoons brown sugar, and 1/2 teaspoon vanilla. Stir until sugar is dissolved and chill. Top with whipped cream. To make the whipped cream, mix 1/2 cup whipping cream, 2 tablespoons confectioners sugar, and 1/2 teaspoon vanilla. Beat until soft peaks form. You can also add a pinch of cinnamon to the eggnog mixture or on top of the whipped cream.