For just such an occasion, you can break out the granola bars. They are just as bad for you as cereal, consisting mostly of oats and honey. They come in a bar, so that you can go on a hike and eat them without making too much of a mess. But if you are hankering for a messy eat, like cereal and milk, all you have to do is break the bar down into smaller pieces.
Then you pour on the milk. It looks just like cereal with milk, and it tastes a lot like it, too.
However, when you do all this in front of your chimpanzee, he will not be fooled. He won't call it cereal. He will call it "granola and milk." But if he enjoys eating it, anyway, your work is done!