It tastes best with whole milk yoghurt and whole milk, but you can also use reduced-fat products. I like to use strawberry jam as a jam.
First you put sugar or diet sweetener, then the jam and yoghurt in a mixing bowl. Then you can fill the yoghurt cup to a third with milk and pour water up to the top, add the liquid to the yoghurt and mix everything up once with the hand blender.
Tastes very similar to the fruit yogurt drinks you buy.