First, sort out the berries, pluck off the stems if necessary and wash.
Bring to a boil with water and simmer for about 5 minutes. Remove from heat and let cool. Stir in the syrup sugar and refrigerate overnight.
The next day, strain very finely, bring to a boil again and simmer for about 3-5 minutes.
Pour the berry syrup into clean bottles and seal tightly.