Is this something that can give horses colic?

Bet your horse loved that cake! Covering the bottom of a 4H candy box with that type of treats would have very little probability of causing colic in a normal adult horse. It wouldn't even be the equivalent of 3lbs of sweet feed. As you now know, you should always be careful about what and how much you feed your horse. Any time a horse gets more treats than normal, remember to cut back on any grain or processed feeds ration for that day to compensate for the *nutrition* derived from the treats.