As long as there wasn't anything artificial in them they'd be interesting to play with. You're right, the sugar would ferment out while hopefully imparting subtle flavors behind.
I've been playing around with flavoring my priming solution at bottling time for that last bit of mouth hit and aroma when you open the bottle. I've done chilies, citrus peels, and even some spices in the boil and strained out after. I decided to add 1.5 ounces of ginger to my priming sugar boil when I did my ginger snap brown ale.
As you can see it has a nice straw color as opposed to the clear you are used to. It smelled amazingly like ginger.
I've also done it with dried chilli peppers for my chocolate mole porter. And done citrus peels with various beers such as using orange peels in my wits.
You could do it with any dry spice, such as cloves, coriander, star anise for a licorice beer, cinnamon and even a vanilla beer. You can do with this is to add some lactose to the boil as well, since it is unfermentable, it should sweeten the flavor somewhat.
I'm planning to try crystallized/candied ginger next time. Evidently it has a sweeter less biting flavor to it.