Icy Poles were the ONLY thing our DS would eat when he recently got really ill. So puree up watermelon, stewed apples, berries, bananas etc and freeze them. You can even freeze yoghurt into them too....It's a great way of getting some nutrition into them when they are feeling SO unwell.
Hopefully he will like that? Hope he is feeling better really soon, it's so hard to see your LOs so unwell.
xx