Bring water to a boil in a small pot over medium heat.
Add sugar and stir until dissolved.
Add blackberries. Cook at a gentle boil for 2-3 minutes or until blackberries are soft.
Remove from heat once the mixture starts to foam and rise up in the pot.
Using a potato masher, crush the blackberries.
Allow the mixture to cool for at least 10-15 minutes or until it reaches room temperature.
Set a fine mesh strainer over a bowl. Pour blackberry mixture through the sieve. Discard solids.
Pour syrup into an airtight glass container.
Store in the refrigerator for up to 2 weeks.