On long mountain hikes (8-10h) with average 2500-3000 m elevation I have bladder with 2 liters isotonic (Isostar or similar) more diluted than recommended doses and honey waffles (lots of calories for little weight
. I also use some cereal-fruit bars and bananas. Drink 0.5l per hour regularly in small sips and eat around 150-200kcal/h, so to valley usually arrive sufficiently hydrated with enough energy.
In between usually eat at some hut vegetable soup with lots of salt and couple bread slices and with it drink half liter pure water. Day before for dinner abundant CHO meal (300gr pasta) and drink lots fluid with it for better glycogen stores.