Wash and sort the fruits. Finely puree the blackberries in a blender.
Put the blackberry puree with water and sugar in a large saucepan, bring to the boil and simmer for 30 minutes. Pour in the two juices 10 minutes before the end of the cooking time. Then filter through a sieve lined with a cotton cloth into a bowl.
Pour into clean, boiled glasses using a funnel. Close tightly and let cool down. It is best to store in a cool place.