Best-ever food for a long day at work with no lunch break, or a long flight or sailing trip or hike:  peanut butter and raisin on homemade whole wheat.  It’s good for those who fortunately have no wheat or nut allergies, tastes good, and keeps you going for a l-o-n-g time.   I think it would even work for a long glider flight.  I once heard a pilot say that peanut butter and honey on wheat is good flight food, but honey gets around, and I can just imagine a sticky control stick, trim tab, water bottle, spoiler handle, and radio push-to-talk button.   If you spread peanut butter on both pieces of bread for PBR, the raisins tend to stay put.  Not perfectly.  After the flight you’d want FOD control.  That’s foreign-object damage control in aerospace speak.  Find the stray raisins before the ants do!