if it is for the surface interval a good cookie (chocolate chip usually) hits the spot. Maybe some watermelon too - and plenty of water or gatorade. though, sometimes during my surface interval i may start to feel a little sea sick I will still try to nibble on something or at least drink water, i just know that as soon as I get back in the water I'll be good again - my sea sickness is instantly gone. It doesn't happen often, and usually only if the seas are a little rougher than usual.
After the dives are done, Five Guys usually is my go-to place (mostly because it is on the way home)