If food gives us energy, then why do we need to sleep?

Because when we sleep, it allows our bodies to recuperate or rejuvenate themselves. Eating does give us energy, but our bodies were created to only take so much until they need to rest. Plus, if we just ate all the time instead of sleeping, we'd all be pretty large.

Eating fat does not add fat, it isnt a poison to be avoided, it is simply high calorie. People who eat a lot of fat usually eat a lot of calories too - removing fat from the diet makes it very hard to over eat. It is a stupid misconception especially since when fat is removed the product is usually processed and replaced by sugar. Slow burning carbs are decent, cereal bars are a good point - try aim for ones without 500 ingredients. But I would also take something like mini cheeses to eat half way through the first day. Mixed nuts are also a decent balance of protein and fat with a bit of sugar too (carbs) I realise you wont eat "anything" but personally if I had to do that sort of thing, the total best food for me would be a plastic jar of peanut butter - I know you mention no spreadable food but 3 plastic spoons would do me, just dig out chunks of it :)

food gives energy in the same way coffee or an energy drink would and sleep just "restores" you :p