Mandatory for your muddy clothes. Folded up in your pocket or helmet, it makes a handy emergency exposure suit for inside the cave. Normally we will not eat in the cave. You might want to take in some small bit of food for extra energy or emergencies. I like chewy granola bars or gorp.
Sandwiches turn to mush without some protection.
Do not drink water from the cave. It is often polluted with fertilizer, herbicides, animal droppings, etc. Optional for Hoofer beginner trips. Don't expect things to stay in your pockets. I use an army surplus butt pack on a shoulder strap.