sugar is bad for everyone not just children
and its in most every processsed food, and it has different names so try to eat as whole food as possible rather than pre packaged.
some of the names its under
dextrose
fructose
glucose
maltose
syrup
avoid food like biscuits, cereals, candy, muesli bars, flavoured chips, yoghurts, and almost all soft drinks.
the other thing is pesticides and herbicides and heavy metals in the food chain. Unfortunatley high concentrarions of this make children vERY sick...adults tend to build up a tolerance but, todays generation are so much more vulnerable to the crap that people have been spraying on crops since after the second world war, thanks to industrialisation and pollution. Food has become so badly adulterated, and arftificial, our bodies cannot even recognise it as food or nututrition any more.
what you can do is eat as fresh food as possible. grow your own is best. Even if you may have to pay more for organic food or shop more often your health may depend on it