Will exercise enhace breast size and what is the exercise or eating soy milk and soy cheese enhance breast size too? I'm 21

Upper body... Upper body exercises that will strengthen and enlarge the pectoralis major and minor will help to give the impression of a larger bust. There aren't any exercises to specifically increase breast tissue, since they are modified sweat glands packed in fat.
These activities. Will not increase your cup size. If you gained weight it is likely that a certain amount would go to breast (but no guarantee). If you develop your pectoralis muscles your breasts will lie differently on the chest (usually in a manner that is attractive to most).