Wash the fruit. Hull strawberries to remove stems, then quarter them. (See Notes section below for tips on using frozen strawberries.)
In a medium saucepan, bring water and strawberries to a boil. Lower the heat and bring to a simmer for 15 minutes. Remove from heat.
Pour through a fine mesh strainer to strain the hot liquid into a bowl or jar. Discard solids.
While still warm, add sugar and stir into the strawberry mixture until sugar dissolves.
Let cool to room temperature. Store in an airtight container for up to two weeks.
Strawberry Mocktail
In a cocktail shaker filled with ice, add strawberry syrup and lemon juice. Shake well.
Strain into a coupe glass. Top with club soda. Garnish with a strawberry slice.
Notes
You can use frozen berries for the strawberry syrup, ideally already sliced ones. Use them like you would fresh ones. If they are frozen whole berries, let them thaw first, then slice them and use them in this recipe. Dehydrated strawberries can be used to make the syrup too.