I don’t know which airline you are using but from my experience I travelled with Emirates a few times, a few years ago. I found them to be fantastic in terms of their special meals they served to me after I had advised them of my dietary needs in advance. They served up really well designed meals and I had the best readings of any time I have been travelling by air. As for snacks maybe a chocolate nut bar, some nuts and a small number of jelly beans on hand if needed. Otherwise the airline should be able to give you some biscuits, cheese and nuts on board to keep for the trip.