Makes 4  servings.
Ingredients
1/2 cup sugar
1/2 cup water
3  cups strawberries, cleaned and sliced
 3/4 cup lemon juice
 4 cups sparkling water or  club soda
lemon and strawberry slices or mint for garnish
Steps

1. Make simple syrup:  Put sugar and water in a small saucepan over medium heat. Stir until sugar is dissolved.  Remove from heat and let cool to room temperature at least 20 minutes or so. (You can refrigerate a little bit.)
2. Put strawberries in a food processor or blender and blend until smooth.  Strain through a mesh strainer.  If it's really thick, take the back of a spoon and push it through the strainer.  (I usually add a little sugar to the leftover part in the strainer and save it for jam!)
3. Put the strawberry liquid and lemon juice in a pitcher and stir.  Add 1/2 of the simple syrup, stir, then taste test.  Add more simple syrup little by little, stirring well.  How much you add will depend on how sweet your berries are.  You can also blend it in the blender.  Refrigerate until very cold.
4. When ready to serve, put ice into glasses, add the strawberry mixture and top off with sparkling water or club soda.  Give each a stir and garnish with lemon slice and mint or strawberry.