My bees did the same thing, just like last year, and the year before. I'm not sure where you are located, but in my case, we are "inbetween" flows. It will remain dead, until the middle of August. The late summer/fall bloom will appear, and honey will be abundant again, especially when the goldenrod comes on.
If you want to try spraying the foundation with sugar water, go for it, but they won't do anything until they have more than enough to feed their brood. You might want to feed them sugar syrup, but even then, they will probably use it for their efforts of raising brood.