In a medium saucepan, combine 1 cup of sugar, 1.5 cups of frozen mixed berries, and ½ cup of water. Heat over medium-low heat for about 10 minutes until the berries soften and burst.

Pour the berry mixture into a blender and blend until smooth. Let the syrup cool for a few minutes.

In a large pitcher, add 2 cups of ice for serving.

Strain the berry mixture through a fine-mesh sieve over the ice in the pitcher.

Add 1 cup of freshly squeezed lemon juice and 3 cups of cold water to the pitcher. Stir well and adjust sweetness if necessary.

Serve the berry lemonade chilled over ice-filled glasses and garnish with fresh berries or mint.