Dh used to work 12 hour shifts so I used to do a cooler bag of stuff for him. He worked in a very physical environment so I could get away with more "fattening" foods. Giving him a huge variety would stop him going to the snack wagon to get greasy foods.

He'd have leftovers for lunch or makins for a sandwich (cold meat, salad stuff, bread, container of butter). Then there would be the snacky stuff

Fruit'n'nuts (usually a tupperware container full)
museli bars
small packs of chips/popcorn etc
tiny teddies/bite sized chocolates
home made bikkies or slices
cheese & crackers

bricks of drink - for helping with cooling
small bottles of ice coffee (usually 2)
frozen bottle or two of water - also helping with cooling