Boil water and sugar until dissolved. Turn off heat. Slowly add dry instant coffee and continue stirring. Add a chopped vanilla bean to the vodka, then combine the cooled sugar syrup and coffee solution with the vodka. Cover tightly and shake vigorously each day for 3 weeks. Strain and filter. Its also best to let the sugar mixture cool completely so the vodka won't evaporate when its added. If you like a smoother feel to the liqueur you can add about 1 teaspoon of glycerine to the finished product.