For an extra burst of flavor, try using chilled red grapes. It will enhance the cooling effect of the drink. Adjust the amount of sugar to your preference, depending on the sweetness of your grapes and açaí pulp. If you don't have a cocktail muddler, you can use the back of a spoon or a wooden pestle. Consider garnishing with a few extra red grapes or a sprig of mint for an elegant presentation.