This is very true. While glycerin is used as a humectant in some applications to keep products moist, under certain conditions it behaves as a desiccant to wick moisture away from an object to keep it dry. In fact, glycerin is commonly used to dry flowers and leaves for use in crafts and decorating. Much of the "water" in vapor comes from our own mouths.
Accordingly, in addition to drinking more water it's helpful to have Biotene in your arsenal. Biotene is an oral product for treating Dry Mouth. It's available as a rinse, gel and liquid. You can find it in the mouthwash section at grocery stores.
For more information about the affects from quitting smoking, this article may be of interest:
Why do my gums bleed now that I've switched to vaping?