Postworkout goals are: 
A ) give protein fuel to your muscle
B ) replenish muscle glycogen 
C ) reduce muscle soreness

That’s why is essential to refuel your body not only with proteins and aminoacids which are not enough if you are dieting to get ripped, but also glucides to replenish your used muscle glycogen  . Citrates presents in fruits help as well to reduce the acidity effect of training. Also the simple sugars and medium chains sugars present in juice and fruits help to faster restore muscle glycogen essential to prevent the use of aminoacids to rebuild it after a heavy workout. A liver and muscles emptied of glycogen are signals of protein catabolism, something we might want to avoid if we want to grow and fill full and ready at the next workout.