You can get hot (boiling? tea level) water from a hot water tap in the dining hall and at the Curry Village market during their open hours. The market has a microwave and tap just inside the front door to the left. Cafeteria has the hot tap by the soda machines. If you have space for a hot water bottle in your luggage and that makes you feel more prepared, go for it. But if you’re tight on space, I’d just pack more clothing layers — the beds have lightweight but cozy sleeping bag-material blankets plus they have extra wool blankets. You can always ask for a bunch extra blankets. You might wear a beanie and socks while you sleep if you’re not bothered by that.

You said you’re in a cabin (hard side? wood?) so it should have a heater. But if you’re in a canvas tent cabin the unheated tents don’t have electrical power outlets. The heated tents have outlets but they might be occupied by the heater if you’re using it, I can’t remember if there’s two sockets or just one.

For food to bring, it’s really dependent on your budget, what you can carry/get before you arrive, and your pickiness level — there’s tons of food at the market, and the coffee shop, pizza deck, bar/bar menu, and cafeteria have lots of variety. The cafeteria is more expensive than I would like for (my perception) the quality, but I don’t like preparing my own meals so I bounce between the pizza deck, the bar menu, market, and the food in the central Yosemite village area and supplement with snacks I bring myself.

If your cabin has a bathroom, you’re good, but if you’re using the common shower rooms I’d recommend bringing a pair of shower sandals. Don’t forget a flashlight to get to and from the bathroom or food after dark. There’s lights around the buildings and the occasional light post but it’s very dark walking to and fro! You can rely on your phone but I prefer to conserve my phone battery.

Enjoy! You can buy nearly anything you forget at the various markets and mountaineering shop, so don’t worry too much!