Mix the freeze-dried coffee and boiling water with half of the sugar. Allow to cool.
In a large bowl, mix the milk and the yogurt or starter sachet, and then whisk until you obtain a smooth mixture. Add the sweetened coffee and mix well.
Pour the mixture into the bottles. Place them in the yogurt maker and cook in yogurt mode for 6 hours.
Once the programme is complete, close the bottles if you have not yet done so and place them in the refrigerator for at least 4 hours. Shake well before drinking.