I do primarily shore diving. Under one of the seats of my truck lives a shopping bag that I keep stocked with a large variety of non-perishables. Some salty, some sweet, some meaty, some carby, because I never know what I'll be in the mood for (jerky, salted and unsalted nuts, chocolate, crackers, chocolate, dried fruit, gummy worms, etc). I also like to bring along some fresh fruit like apples or bananas. One of my dive buddies often brings deli sandwich ingredients, for which I am always very grateful, but usually can't be arsed to do myself.
Boat diving is another story, because not making a mess, taking up too much space, or just irritating others becomes a bigger concern. I like to make a small stack of peanut butter + jelly + nutella sandwiches. Because it's easy on the stomach, somewhat nutritious, cheap (so you can bring twice as much as you think you need), and you won't be too sad if they get smushed under some dive gear. And it hits the spot.
Boat diving is another story, because not making a mess, taking up too much space, or just irritating others becomes a bigger concern. I like to make a small stack of peanut butter + jelly + nutella sandwiches. Because it's easy on the stomach, somewhat nutritious, cheap (so you can bring twice as much as you think you need), and you won't be too sad if they get smushed under some dive gear. And it hits the spot.