Back in the 80's, usually, all I carried in my jersey back pockets were my driver's license, for ID , a house key, a couple of bills (10-20 bucks) and a bit of change for pre-cell phone era phone calls., tube patch kit (Rema) and a couple of plastic tire levers..... sometime I had my cycling cap or a ski cap back there, depending on the weather. Can't remember ever carrying any food, as I usually bought it while out riding.