Clean your chosen fruits or mix of the 3. Cut them into small pieces and pour them in a deep oven dish.
Pour the preservative on top and then the water. Put it on the stove to boil, while stirring occasionally. Once it comes to a boil, add the sweetener and finish boiling for another 5 min.
Remove from the stove - at this stage the jam will be runnier than usual but after it cools it will thicken and gel.
Distribute it immediately into jars, close them and turn them upside down until fully cooled.