Wash the berries thoroughly and clip the coarse stems off the clusters. Cut the apples into large cubes and place them in a pot with elderberries and water. Turn on the heat and let the mixture come to a boil until the berries burst and the apples cook down. Now hang the elderberries and apples to drain in a juice bag or place a thin piece of cloth in a strainer, so the juice separates from the fruit. A tea towel works fine, but let the expensive ones stay in the drawer, as elderberries stain terribly! Once the last precious drops have dripped out, pour the juice into a pot and add sugar and lemon juice. Bring to a boil and skim off the pink foam that collects along the edges of the pot. Adjust the taste with sugar and lemon before pouring the finished juice into sterilized bottles. Elderberry juice stays fresh in the bottle for several months, but you can also freeze it without any problems. Opened bottles should be stored in the refrigerator and consumed within a couple of weeks.