well I have feed deer about everything there is, from donuts to candy
so yes they like sweet things
but I don't think th added cost is worth it
many of the horse feeds are alfalfa based, whick pending the cut and time of yr will make a big difference on how well the deer eat them
but some are actual sugar cubes and the like, so all depends on what exactly type of feed your talking

to me, if I wanted to do anything I would buy a 10+ lb bag of sugar and sprinkle it on top of the corn, heck I would add table salt too
maybe mix the two together, and then ad a few lbs to every 100 lbs of corn
ONLY the salt will be hard on any metal parts of a feeder

you can also buy a bottle of honey/maple syrup or even the strawberry syrup and pour some on the corn too
a bottle will last quite long if you add some once a every few days or so too!
I do that to get bear pictures if I want them
but always get deer eating the corn first!