I get drunk from eating sugar too. It started 6 years ago and after multiple test there is no diagnosis yet. I get sick from any carbohydrates, but sugar leads to a quicker high. The worst is high-fructose corn syrup or honey. After the "drunk" I feel horrible. My liver area and kidney area hurts. I also have arthritis since this started occurring. I have an elevated heart rate during the "drunk". One test that did show results was testing hematocrit levels during the diabetes tests, those levels jump sky high, which indicates "dehydration".
My guess: I have an organism (perhaps fungal) that thrives on sugar. When it is fed sugar it produces a byproduct that is poison to my system. My body goes into overdrive to get rid of that poison and uses all of the water in my system to rid my system of the poison, thereby dehydrating me. Dehydration causes the "drunk". The sick feeling afterwards is due to the processing of the poison by my liver and kidneys.
I remember not feeling this way, but your nephew is so young that he probably doesn't remember ever feeling "well". I believe that your nephew is generally very unwell except for in the morning before he has eaten anything. A diet of protein and greens can make me feel good, but it is a diet that is very difficult to stick to and lacks the vitamins that fruit, root vegetables, and grains provide.
I am very interested in any research in this area. I, also, suspect that many who are sick with undiagnosed malaise might be harboring the organism that I have and do not realise that food is making them sick.
If anyone has had this and knows of an effective treatment please post any suggestions. I will try most anything!