First, a berry syrup is made. To do this, put the berries, the juice of the lemon and xylitol in a saucepan and boil it down over a medium heat for about 5 minutes until the xylitol has dissolved and the berries have boiled over.
Press the mixture through a sieve so that all of the seeds remain.
For the lemonade, put the syrup, mint leaves and ice cubes in a pitcher. Top up with still or sparkling water as desired.