Nowdays on Oahu seem like the most likely occurance is getting stuck in traffic when HPD shuts down H-1 or other highways for hours.  For this, some hard candy,

The car kits I have are vacume sealed flat pack so the can tuck out the way.
In my work van, I have gum, tuna in foil bag, juice powder, socks, tissues, papa cord, camp sisicors, first aid kit (focused on walking home) water purification tablets, sun screen (2 time use packet) hand sanatiser, 2zip lick bags, a razor blade. It's all vacume sealed in a book bag (the cheap ones with cord for straps) I also have water in my door panels and an extra first aid kit in my glove box.

My wife's car and my other car both have extra stuff because usually we have 2-3 people in it.

I would also have in the car a change of clothes (T-shirt shorts underwear).  Our set helped us when they shut the freeway down when the the walkway over the freeway in Aiea was hit. We stayed with a friend in town.