After your workout is over, your muscle cells will be crying out for nutrients. This is THE BEST time to utilise fast carbohydrates as well as a good quality protein source for muscle recovery and growth.
You need carbs post workout – preferably liquid with a high glycemic index (like Vitargo but it depends on what you have available, see the supplements section for more information).
You need protein post workout; immediately post workout (whey protein shake) and more around 2hrs after from a lean protein source.