Combine Ingredients: Add 1 cup water, sugar, and blackberries to a saucepan.
Heat the Mixture: Bring to a gentle boil over medium heat.
Smash the Berries: Use a fork or potato masher to release the juices.
Dissolve the Sugar: Cook for about 2–3 minutes until sugar fully dissolves.
Cool Slightly: Remove from heat and let it rest for a few minutes.
Strain the Syrup: Pour through a fine strainer into a pitcher and discard seeds.
Add Lemon Juice and Water: Stir in lemon juice and remaining 3 cups water.
Chill and Serve: Add ice and enjoy cold.