How do I give my brother some food for thought about his son without seeming like a holier than thou dork ?

Here's the thing : his son is about 6 and his school teachers are recommending that my brother give him Ritalin to help him focus.
Although what I see is that his kids are addicted to sugar. My bro makes lots of money and his kids have everything they could want and more. This includes a kitchen full of sugary things. When I walk into their kitchen the smell of sugar hits me straight away and my mind wants it. The cupboards are full of every sugary thing that you could want.
I suspect that this is affecting his son's ability to concentrate and I'm worried that Ritalin will be doping his mind just to counteract the constant sugar rush.
On the other hand his wife is really large because she uses sugary foods all day long as comfort food because she is stressed. So she is basically setting the example for their kids. I do sympathise with her though.
He is in an awkward situation and I don't want to stick my nose into it and cause trouble. I'm concerned for the wellbeing of his son though because he has great potential. He needs to stop eating sugar in my opinion for his own good.

What do you think ? Give the kid Ritalin or discipline the kid and his mother to stop the sugar addiction ?