I was going to say HFCS - but since you've got that, you might also consider the preservatives in food? Just from my experiences, in the States it seems like preservatives are in everything!!
One thing I'd suggest, find a place like Whole Foods or Trader Joes and stock up on things like granola, nuts, easy/quick energy foods?
I have major food issues so I go on really bland diets when I get ill (oatmeal, tea, toast, chicken/salmon & rice or pasta, plenty of uncooked veggies) and find being on a routine where you know exactly what is in everything you're eating is super handy to figure out. It's quite dull, but at least you feel better fairly quick.