Chiming in late. If my mare is risking impaction colic by not drinking enough I make her a ten gallon bucket of warm water with molasses and salt. It has the sickly sweet salt taste of blood or that sour dutch licorice but she will drink it down.
My barn friend was experimenting with a bunch of herbal teas and the horses loved them too
I’m after volume with the warm molasses salt so using basic stuff I have on hand