Wash and clean the elderberries thoroughly. Cut off and remove most of the branches and twigs. You can leave on the smallest ones.

Wash the apples and remove the core. Slice them.

Put the elderberries and the apples in a large saucepan and add all the water. Let it boil for about 30 minutes or until all the juice is extracted from the berries.

Put a clean tea towel or similar inside a strainer. Place the strainer on top of another large saucepan or bowl. Pour the elderberry juice in the strainer and use a spoon to press the berries so that you get all the juice out of them. Let it sit until all the juice is passed through the tea towel and strainer.

At medium heat, heat up the concentrated juice in a saucepan and add the sugar. Continue heating and stirring until all the sugar is dissolved.

Clean some bottles in very hot water (preferred boiling water), and let them cool off. Pour the concentrated elderberry juice on to the bottles and close/seal them right after. This step is important if you want to make the juice last longer.

Keep the juice refrigerated. You should be able to store it for quite some time. I believe when you have opened a bottle it will last for a couple of weeks.