I'm so sorry that he's having so much trouble trying to eat. After rads, all I could stomach for awhile were varieties of high calorie milkshakes and green juices. I got sick of having any one particular thing, so I just had a giant pail of vanilla ice cream, milk, and flavoured my shakes with whatever I felt like at the time (so chocolate, coffee, peanut butter, cherries, blueberries, coconut cream, bananas, peppermint extract, green matcha, etc.)

If he's craving cake, you can probably make a milkshake similar to whatever flavor of cake he might be craving. I personally don't like icing, but maybe its all that whipped cream and candy sprinkles that he's after. You can add those to the blender.