Hogs are apt to eat just about anything organic. I say "just about" because for three years running, I tried free leftover pumpkins and nothing touched them. They rotted in place.
You could try the grounds, but I would try it away from places where you have feeders and the like. Find a nice clearing and dump out a bunch of coffee grounds and set up a game camera and see what happens. If the come to it and eat it, then you may be onto something. If you try the grounds where the hogs are already known to be coming, then you don't know if it was the grounds that attracted them or the fact that they showed up as they might normally do and just happened to find the grounds.