make a fruit puree and serve it in an egg cup. Provide peeled sticks of apple, carrot and cucumber.
Now, this is the important part.
Serve it only to yourself.
Don't serve him any. Serve it to you,and ideally somene else who will talk to you appreciatively about how tasty it is. Have a little giggle of joy whilst eating it. Ignore him unless he asks for some, don't offer it.
Then once he is good and interested, leave the room. Leave the fruit and fruit dip behind. Peep at him through the door if you can do so without being noticed, but don't give him a clue that you're watching him.
I think there's a 50/50 chance he's want to see what all the fuss is about.
Oh, and stop giving him sweets, cakes, biscuits and puddings, and juices. YOu want that tasty fruit plate to be the sweetest thing he EVER tastes.