Peel and segment 4 of the fruits. Juice the last one.
Stir 4 tbsp of water in with sugar in a microwave bowl. Microwave the sugar on High for 4-5 mins until everything is bubbling and golden. Using a cloth or oven gloves, carefully remove the bowl from the microwave and stir in the fruit juice – watch out, it will splutter. Stir in the segments and serve alongside the slices of cake and yogurt.