This refreshing sip gets tang from citrus and sweetness from fiber-filled blackberries. Make it a mocktail or spike each glass with a little tequila or rum.
Bring 1 cup water to a boil in a small saucepan over medium-high; stir in sugar. Remove from heat; let cool completely, about 30 minutes.
Place blackberries, lime juice, orange juice, and cooled sugar syrup in a blender; process until smooth, about 1 minute. Pour mixture through a fine mesh strainer into a pitcher; discard solids. Refrigerate until ready to serve, up to 24 hours.
Place 1/2 cup ice in each of 8 glasses. Pour 1/4 cup blackberry syrup into each glass, and add 3 tablespoons tequila or rum, if using. Top with 1/2 cup sparkling water. Garnish glasses with whole berries.