01 - Combine grapes, water, sugar, and lime juice in a blender. Process on high speed until completely smooth and frothy.
02 - Pour blended mixture through a fine mesh sieve or cheesecloth into a pitcher, pressing to extract all liquid while removing skins and solids.
03 - Taste the agua fresca and add more sugar or lime juice as needed to achieve desired sweetness and balance.
04 - Refrigerate until thoroughly chilled or serve immediately over ice. Garnish glasses with fresh mint sprigs or additional grapes if desired.