There is a number of factors you need to replace when you have been exercising at a high level or any level in general.
Now, if you have been on a long distance run, you have been sweating because your body naturally releases water out of the body to regulate your body temperature, so as you run, the sweat passes over the skin and the wind cools your body down. That there is an element of hydration from the body, that is water that has come from within, so therefore, we must replace that water with electrolytes and with general water, because your body will burn both in order to keep you fuelled while you were running.
Now, electrolytes, you can get from any sort of source of like sugary or electrolyte supplement. What you need to remember is just replace in general, what you have burnt. Now, when it comes to fixing the body, now we talked about previously is protein, protein are those building blocks that are going to allow the body to recover from the intense exercise it has been through.
Now, when you are running, your body is still going through the muscular tension movement, so therefore, you are getting the micro-fibre tears. The tears need the building blocks from the protein, so when we finish a run, for example, try and get a nice protein source in there, protein bar or a nice protein source of meat out of the fridge that you have got prepared from the morning earlier.
Carbohydrates. Now, when it comes to carbohydrates, they are a huge factor when it comes to letting the body perform on fuel. Now, if you burn them off during exercise and you are looking to maintain your body weight, then you must replace those calories, otherwise you are going to find yourself in what we call a calorie deficit. And a calorie deficit is the only place you want to be if you are trying to lose weight. If you are trying to lose weight, that is absolutely fine, that's probably one of the reasons why you are exercising, so maybe you do not need to replace those calories instantly, but if you are not looking to be in a calorie deficit, then you must replace the calories that you have burned during exercise.
Now, when it comes to preventing stuff like cramps, I would recommend a banana to get your potassium levels back up. I would also recommend bringing tonic water into your body, because that will help prevent cramp in the future.