Is it possible to grow taller using specific methods? i'm asking for a friend who is still in puberty(15)

None under ur contro: Growing taller depends upon genetics, adequate nutrition (check out difference in height btwn average North & South Koreans), growth plates & more. However, there are no specific methods aside from getting enough to eat, getting enough exercise & getting enough rest, to make oneself grow taller than predetermined.

Healthy lifestyle: You are most likely to reach your tallest potential height by following a healthy diet, getting appropriate sleep & and remaining physiclly active.Nothing you eat or drink will add inches & normal kids who get hormone injections just get to their final height quicker, it would not add to final height.You can stunt your growth by the opposite, poor diet/sleep/inactivity can all take a toll.