Make a mini fire in the bottom of a coke can
Coke Can (cut in half and edges folded of filed so they are not sharp)
Twigs, leaves, paper
Gather some twigs, dry leaves, scraps of paper and build a mini fire in the bottom of the coke can.
Try and light the fire. Whose burns best, brightest, highest?
You could cook marshmallows and make mini-smores.