The first energy source consumed when doing physical exercise is the glucose in the blood; so, eating foods rich in carbohydrates within 15 minutes of finishing your workout will increase glycogen reserves in the muscles and liver that have been depleted while doing exercise.
On the other hand, proteins help grow, develop and maintain tissue, giving us the amino acids we need to help build and repair muscles.
Plus, they are effective in restoring glycogen levels so they shouldn't be left out of a post-workout snack because, in conjunction with carbohydrates, they help deliver glucose to the muscles.
So, to answer the question: what is best to eat after doing exercise? We would say that carbohydrates and protein is an excellent combination after a hard workout.
Some examples of this combination include: