01 - Combine grapes, water, sugar, and lime juice in a blender. Blend on high speed until completely smooth and frothy, approximately 1-2 minutes.
02 - Pour blended mixture through a fine mesh sieve or cheesecloth into a clean pitcher. Press solids with spoon to extract all liquid. Discard pulp.
03 - Taste the agua fresca and add additional sugar or lime juice as desired. Stir thoroughly until dissolved.
04 - Refrigerate until thoroughly chilled, approximately 30 minutes, or serve immediately over ice. Garnish with fresh mint sprigs or whole grapes if desired.