I have the same doubt with food offerings, I usually keep them in the altar until some of my pets passes by and eat it when I'm not looking. But sometimes it just doesn't feel right to keep it there, but eating it doesn't either.
Just out of curiosity, what are you going to offer him?
What you do with your offering depends on your environment. For instance some if possible burn their offerings and others bury them. Other methods I've read about involve simply leaving it in nature, composting it if that is possible, etc... For one it would depend on the offering itself as some offering, such as you mention candy, would not work well to be burned, composted, or given to animals/nature.