In a medium saucepan, heat sugar, 4 cups water, and strawberries over medium heat until sugar dissolves and strawberries soften, about 5 minutes. Let cool to room temperature. Strain mixture through a fine-mesh sieve in a large bowl; discard strawberry pulp.

In a large pitcher, combine lemon juice and sugar mixture, stirring to combine. Serve over ice. Garnish with lemon and strawberry, if desired.