Advice??

We have been having a terrible time getting Zenock to eat his food. It seems the only thing he never complains about eating is rice krispies, cheese, and water. Brady and I are really frustrated right now because we have tried everything. Bribery used to work, but not anymore. And to make it worse, when he gets really worked up he starts coughing and gagging, so then he throws up. If there is anything you all can think of to help him not be so dang picky I would certainly welcome suggestions. Thankfully Ammon eats really well!