First, hydrate to replenish the fluid you’ve lost from sweating. A good rule is to drink 16 to 24 ounces for every pound you lose over the course of your run. That’s slightly more than what you sweat and pee out. Plain old water should be fine, as long as you are planning to eat something soon, which you should.
Then refuel your body. Your post-run meal should be a mix of carbohydrates, to replenish your glycogen stores, and protein, which helps muscles rebuild. You should strive for a 3:1 ratio of carbs to proteins. Chocolate milk is heralded as a perfect recovery fuel, because it has that balance, but you can eat solid food, like a turkey sandwich, too.
It’s particularly important to eat after your run if you’re planning to run again soon. For instance, if you tick off your long runs on Sunday afternoons, then know you’re going to get up and run before work on Monday morning, make sure you’re properly fueled before you go to bed.