If you want to feed some extra goodies once in a while, I recommend buying different fruits and veggies and experimenting with what they like best. Mine like zucchini, cantalope, pears, broccoli, and of course carrots and apples. If we have one of those for dinner or lunch, I'll save a bowl for them. Or when I clean the fidge, if there are leftovers that are still decent, but I know we won't eat them, I'll toss them in the feed buckets.
If you want to feed them something hot, make some soupy oatmeal and toss a couple of peppermints or some raisins in it.
Daily I feed my horses my own mix of alfalfa pellets, whole oats, 1 cup of milled flax (Nutra Flax from horsetech.com), and a vitamin supplement. I don't like feeding sweet feed or pelleted feed, too much sugar and byproducts.