Eating, drinking and sleeping can be problematic. I wish I had an answer because I'd be doing it!
My appetite went too. It grieved me to look at cakes and just feel sick! I get sugared out quickly and easily, so try and vary my snacks and eat little and often on the bike. Not for me plate fulls of food at each control, they just sit heavy unless I sit around for hours I can't afford. So if I'm going to eat larger portions, its before sleeping. Some say you have to force yourself to eat, I can't do that and left half a plate of beans on toast at the Honeybourne control.
Service stations can be a mecca. They sometimes have a selection of savory stuff like pies, scotch eggs, etc. Scan the shelves and let your palate be your guide. Any food is better than none. At Muxton, I couldn't face McD's but found some very acceptable deli-style chicken bits in the service station.
With drinks, I can't do any kind of sports drink. Again, I feel sick. So it's just plain water for me. And I tire of that too! So it's the occasional small bottle of apple juice or whatever takes my fancy just to break the taste.
Sleep, well, not a good subject for me. I'm not fast enough to bank enough time to get the sleep I need. I have to ride buzzy headed and foggy to complete in time. It's not good and possibly the biggest motivating factor in my decision to stop the big rides. I just don't think it's safe.
Others don't seem to have that problem and can function on a few hours sleep, or they simply accept it as part of the challenge (and that's fine and their call to make) but IMHO you have to seriously ask yourself how important are rides like PBP if you need your sleep.