I'd say it very much depends on how often the water stations are and how often you need to drink. Also the conditions will make a big difference. In October it could be quite a warm day where you would need to drink more often?
My diet is fairly good (I think!!). I calorie count a lot of time but also try and ensure that I get a good proportion of fruit/veg and try to steer away from processed food as much as possible (I'm not obsessive about this though).
A typical day
Breakfast: 2 Eggs scrambled (no butter) or Berries and Greek 0% Yoghurt or a granola bar (when I have no time!)
Mid Morning: Something from my graze box: handful of nuts, some dried fruits etc
Lunch: Big mixed salad (including chick peas) with lite mayo and 2 boiled eggs OR a granary baguette with salad and avocado
Dinner: Chilli and rice or Steak and Sweet Potato with roasted veg
I drink black coffee and drink about 1 litre of water a day (I aim for 2 but often forget)
I usually have an apple or a banana at some point during the day.
When I have a race I tend to have wholemeal pasta with mixed veg and a tomato sauce for dinner the night before. I do have this at other times too and it doesn't have any ill effects then. I have a bit of a race day routine now whereby I get up at 6am and have breakfast (I either have a granola bar or some porridge) and I then have 2 cups of coffee quite quickly as this tends to make me 'go'. Then I wait until about an hour before the race and take 2 imodium!