Halve the vanilla pod, add sugar and water to a saucepan and bring to the boil. Let simmer for about 1 minute, remove from heat and let cool down for 10 minutes. Take out the vanilla pod and scrape out the pulp with the back of a knife, add this back to the syrup. Then put this in a blender and mix with the apple juice. Add the yogurt and mix until everything is thick.
Fill the glasses with ice cubes and top up with the vanilla smoothie.