Add 1 cup of water and the sugar to a small pot and simmer on medium-heat until the sugar has dissolved. Add in the blueberries and simmer for 3-4 minutes on high-heat until the blueberries are somewhat mushy.

Strain the blueberries using a cheesecloth. Set aside the blueberry syrup until it has cooled. Once the blueberry syrup has cooled, add 4 cups of water. Mix in the freshly squeezed lemon juice.

Store in the refrigerator to allow it to chill.