Combine water and sugar in a small saucepan. Bring to a boil, stirring occasionally until sugar is dissolved, about 5 to 10 minutes.

Stir in frozen raspberries and return to a boil. Remove from the heat and mash mixture using a fork.

Drain mixture through a fine mesh strainer, pressing raspberry pulp with a spatula to extract as much liquid as possible. Discard solids and refrigerate syrup until cooled.

In a large pitcher muddle mint and fresh raspberries. Add lemon juice, cooled raspberry simple syrup, and sparkling lemonade for a sweeter taste or sparkling water, and stir to combine. Add enough ice to fill the pitcher.