Combine strawberries, sugar, and water in a medium saucepan. Bring to a simmer over medium heat, stirring until the sugar dissolves.

Reduce heat to low and continue to simmer for 10-15 minutes, until strawberries are soft and the syrup slightly thickens. Mash the strawberries with a fork or potato masher.

Remove from heat and let cool slightly, then strain the syrup through a fine-mesh sieve into a clean jar or bottle, pressing on the solids to extract all liquid. Discard the solids and chill the syrup until cold.

Fill glasses with ice. Add 2-3 tablespoons of strawberry syrup to each glass. Adjust the amount to your taste.

Pour cold sparkling water over the syrup and add a squeeze of fresh lemon juice. Stir gently to combine before serving.