I've stopped smoking (almost, mostly) and drinking (regularly, or every night) and I don't take any drugs; I don't drink much coffee but I drink a lot more water than before and in a consistent fashion. This ought to help, right? What should I eat and when?
all that stuff is indeed good & ought to help.
as far as diet, there's a few things. lots of fruits & vegetables, leafy greens (kale, spinach, chard, etc - tons & tons of iron, which is good for combating fatigues) especially. in general I try to get most of my carbs from fruits & vegetables rather than from bread, rice (esp. white), potatoes, pasta, etc tho I do eat quite a bit of oatmeal. low-fat protein sources like chicken (not fried, mind), turkey, fish, egg whites, but no red meat. nuts & seeds, also nut butters (if peanut butter, the real stuff rather than Jif or whatever). no or v. little refined sugar - no sweets, no soda, and so on. refined sugar is like f**king poison. be on the lookout on labels for words like sucrose, maltose, corn syrup, which all just mean sugar. this is also the reason for avoiding refined carbs from bread, pasta, etc (esp that made from white flour) which quickly break down into simple sugars in your body. also be on the lookout for sugar in foods where you wouldn't expect it.
as to when, multiple small meals are always preferrable to one big meal - keeps the body's blood sugar steady - this is why, for example, if you eat a bunch of refined sugar you'll get a burst of energy & then crash. I try to make sure every small meal is relatively balanced.
of course, every person is slightly different. for example, I run, do fairly serious weight training multiple times a week & train muay thai almost every day, so I eat quite a lot, including quite a bit of protein. other people's needs will be different, based on age, weight, metabolism, level of activity & so on. it depends on what your goals are as well. I mean, I'm really strict about it - I drink a beer once in a while & I occasionally drink coffee, but that's about it, & I never eat sweets. not everyone will want to take it that seriously, & that's absolutely fine. still, I think all of the above is general advice that anyone can utilize - you just have to gear it to your own needs.
sorry, I don't mean to go on & on but as you may be able to tell this is a subject about which I'm fairly passionate & I tend to nerd out about it the way some dudes nerd out about obscure dancehall 12"s or particle physics or whatever. hope some of it helps.