Horse treat recipe?

Hi all,

So my horse has taken up a new hobby of dragging his water bucket away from where it is kept and drinking the water off the ground... (He's special) And I'm guessing it's from boredom, so I got one of those treat balls and it seems like that will keep him occupied for a while. I am just wondering if anyone knows a good recipe for treats so I don't blow through my good ones that will last a while? Grain could work, but I think that could make him intake more sand than I would like (we already have a sand-in-gut-problem, possibly from drinking water off the ground :shock. I've tried the molasses and oats recipes but they only last for a week at the most. Would doing something like soaking some grain in water or something and then baking it work?

Thanks in advance!