jkurz is right, theres no supplement that is going to help him with gaining weight if hes not eating properly. And he absolutely is not, as he is having this problem.
If he can do that tell him he should run for mr. Olympia in a few years. But on a serious note, you need three essential things to gain muscle massand become "faster"... Adequate nutrition/surplus of calories, Weight training/cardio , and sleep. Tell him to give you a typical meal plan for a day, post it on here and then we can go from there. If it was just as simple as taking a supplement i think there would be a lot less people searching on bodybuilding forums.