Twist-off jars are best for this as they close airtight. Boil the jars and the lids from them beforehand. Also lay out the cling film.
The calorie information relates to a filled glass.
Wash and dry the lemons. Now cut the peel of 5 lemons into fine strips (works best with a zest ripper). Squeeze all 10 lemons and pour the juice into a measuring cup. Fill up with enough water to get 3/4 liter of liquid. Add the lemon strips and put everything in a saucepan. Sprinkle in the preserving sugar and bring everything to the boil while stirring. Let it simmer for about 4 minutes, then stir in the whiskey and immediately pour into the prepared twist-off glasses. Pull the prepared cling film through the rum, place it on the glasses and screw the lids tight. Turn it over and place on the lid for approx. 5 minutes. Then put it back on the floor and let it cool down for good.