Hi Hobbitfeet,
In the west the Water Apple is also know as the Rose Apple, it's local name is Jambu, with the most common being called Jabu Air, meaning water jambu. It doesn't really have much flavour, just a slight sweetness when eaten and it has a slightly sweet aroma also, however the flowers have no scent that I have been aware of.
The Indonesians most commonly eat Jambu Air as part of a tart fruit salad called Rujak, which is a collection of slices of different fruits, such as Sour Mango, Jambu, Pineapple, unripe Papaya, and a small cucumber called Timun, these all being sliced thinly in bite sized pieces and eaten together with either a sauce made from palm sugar, hot red chillies and belachan (fermented shrimp paste) or just with ground fresh red chillies and salt.
Rujak Picking and dipping as they proceed through a communal bowl of fruit, you will often find the ladies of the neighbourhood eating this as an afternoon snack all sitting around one neighbours porch or doorstep sharing all of the latest gossip.
Here is a link to a description of the fruit and tree:
http://www.dnull.com/jambu-air/Regards,
Richard