If you follow my school lunch posts, then you probably know how big of a hit sandwich bites, or sandwich squares are with my daughter. I pack them quite often, they are just perfect and bite sized, and I actually feel like kids are more likely to finish a sandwich when it's cut in this way. I use a FunBites cutter to make them.
So, in the thermos there was some Annie's Organic mac and ceese, then I packed the sandwich bites on heart food picks, and some strawberries. For the sandwich bites just pick whatever kind of bread and spreads you like, and assemble the sandwich, use the FunBites cutter and then slide the pieces onto food picks.