I have left my chickens for 5 days once when I went to Alaska. My dad was at the farm and did a quick eyeball of everyone a couple times, but he didn't actually feed or water or do anything with them. I filled up a couple of big flat ruber horse feed pans with mixed feed (sunflower seed, cracked corn, layer pellets, oats) The total feed equated to probably 25 pounds. Whatever they scratched out, they could just eat off the ground. I filled up several large flat rubber pans for a total of around 20 gallons of water. I set the water in the shade so it would never be exposed to sun (algae) and it was fine. Mine were free ranging at the time also, but if they were locked in a pen and coop, I would put in some fruits and vegetables, but not too much that it rots and becomes a problem. I would probably cut a big watermelon in half because that can last a small flock of around 15 birds for a couple days. You can cut apples in half, and give them a couple heads of cabbage, which they love. For leaving them alone in the winter, you'll have to give them heated water bowls, and those are smaller. The biggest ones I have, only hold 2 gallons.
Another thing I found that keeps my chickens busy all day is sprinkling dried meal worms all over their chicken house and run floor. They spend the whole day rooting out every little dropped worm from every crook and cranny.