Add 300ml to a large pot and bring to a simmer.
Add sliced apples and lemon juice. Cover and simmer for 15 minutes.
Add the sugar, then boil until thickened. Stir constantly to stop the mixture sticking.
Finally, add the cinnamon, then put the mixture into jars and allow it to cool.
Once cooled, close the lids tightly and store in a cool, dry place.