People are surprised by the food on Kilimanjaro, and then surprised again when they stop wanting it.
What the cook produces
More than you'd believe from a tent and a gas burner. Porridge, eggs and fruit at breakfast. Soup to start every lunch and dinner, then rice, pasta, stews, chapati, vegetables, sometimes chicken or fish lower down. It's carbohydrate-heavy on purpose, because that's what you're burning. The soup is the thing everyone remembers, partly because it's good and partly because it's the one thing you still want at 4,600 metres.
How much water
Three to four litres a day, and more on summit day. This isn't optional advice. Dehydration at altitude produces headaches, nausea and fatigue that look exactly like altitude sickness, and people get sent down for symptoms that were really just not drinking enough.
The crew collect water from streams and treat or boil it. Bring your own purification tablets or a filter bottle as a backup if that matters to you. Carry three litres of capacity: a bladder is easy to drink from but the tube freezes high up, so bring at least one wide-mouthed bottle as well, and on summit night carry bottles only.
Why your appetite disappears
Altitude suppresses hunger, and by day five a lot of people have to make themselves eat. Do make yourself. You're burning a lot and you can't catch up later. Snacks you actually like are worth their weight: bring your own from home, because what sounds nice at sea level and what you can face at 4,000 metres are different lists. Salty is often easier than sweet by the end.
Dietary requirements
Vegetarian is routine and done well. Vegan, gluten-free, allergies and religious requirements are all workable, but they have to be known before the shopping is done, not mentioned at the gate. Tell your operator when you book, and be specific, because the food is bought in town and carried up on someone's back.
Tea, and lots of it
Tea, coffee, hot chocolate and ginger tea appear constantly, and ginger tea is the standing remedy for a queasy stomach. Alcohol is a bad idea at altitude and most crews won't carry it.
The unglamorous warning
The commonest illness on the mountain is a stomach bug going round a mess tent, not altitude sickness. Use hand sanitiser before every single meal. It's the cheapest insurance on the whole climb.
Summit night is different
You'll be woken around eleven for tea and biscuits you won't want, and you should eat something anyway. Carry snacks you can get into with gloves on and that won't freeze solid, which rules out most chocolate bars and rules in sweets, dried fruit and energy gels. Water freezes in a bladder tube within an hour up there, so carry bottles, insulated or upside down.