What yeast or other bugs are involved? If you kettle soured it, the acid production is done, your yeast is still active and the sugars in your fruit flavoring will all turn to ethanol. Ditto if you used hop-intolerant bacteria and then added hops to stop souring. If you are using acid-producing yeast (Sourvisiae, e.g.) then the sugar will be turned to both ethanol and lactic acid, so while you'll add sourness, the sweetness will all be gone.
If you fermented with yeast and soured by adding bacteria, you're working at a higher level than I function. Not sure the yeast will still be active to eat the sugars, not sure the bacteria will do it completely in a reasonable amount of time.
Another option to amp up the flavor is to freeze-concentrate the beer.