Also, for purposes of this discussion, I am targeting people like me: the recreational athlete who does all this for personal fitness and fun. If you aspire to elite status or some other greatness, go read Chris Carmichael's blog. That said, here's the skinny.
Pre Workout: Water, water everywhere.
Your body can't work well without water. So drink up. You can't make up for what you didn't drink before a workout during a workout, so your water intake needs to be consistent. There's lots of fancy formulas out there about how much you need to take in based on your body weight, activity level, and all that stuff, but a good rule of thumb is your urine should be pale yellow. Darker? Drink more. Clear? Drink a little less.
Pre Workout: Kiss my Grits.
If you've read Christopher McDougall's Born To Run, he waxes rhapsodic about "pinole," the ancient Native American superfood. Southerners have known about it for a long time. Pinole is a fancy name for grits. Coarse ground nixtamilized corn: yep, that's grits all right. There's something about the nixtamilzation that activates all the good stuff in the corn, so corn meal will be a pale substitute for the real thing. Try them; I like them with a little butter or cheese (like a teaspoon) and some salt (for the sodium you'll need). Yum.
Pre Workout: Monkey Bidness
Also, you'll need potassium before you go. The cheapest and most effective way to do this is to eat a banana. If you can't stomach that, try coconut water; it's a little more expensive (about a buck for a serving) but very high in potassium.
During Workout: Redneck Shot Blocks
Let me first say that you will probably not need to eat during a workout until your workouts begin to exceed an hour. However, if you find that your energy flags or you begin to get irritable about 30 minutes in, it may be a blood sugar issue and a little something-something may help.
You can buy expensive gels, candies, and other stuff that contain a bunch of weird ingredients, and those are fine, but you can get the same effect by taking some cheap jelly candy (gummy bears, those orange slices with the sugar on them, or sour patch kids), lightly dampening them, and rolling them in salt. Let them dry, and you can pop one in your mouth if you are flagging. The salt will help replace the sodium you're losing, and the sugar will help with energy levels.
During Workout: The Army's Solution To Everything
Which is, according to my brother, "Drink More Water." Feeling dizzy? Drink more water. Aching calves? Drink more water. Broken arm? Drink.More.Water.
Not really, but yes, you need to drink if your workout exceeds an hour, and some people (like me) need to drink if the workout exceeds 30 minutes.
Post Workout: Chocolate Milk (Yessssss!!!)
Seriously, even the personal trainers will tell you this is theee recovery drink. Something about the ratio of carbs, protein, and fat, blah blah, but I can tell you, I don't really need an excuse to drink chocolate milk. Yum.