Flyin Dutch and ginge, oh dear. You clearly have no idea of whats going on in the real world. Nearly all normal teenagers will experiment with drugs at some point, should they all seek a less responsible career. Stick to the moral high ground chaps drinking G & T and smoking safe in the knowledge that you dont "do" drugs.
Redbull your friends steriod use wont show up on the medical and is no problem after this lenght of time but due to a number of factors a current pilot should not use them (mood, fatigue etc).
The milder and legal Pro hormones will affect a proportion of the benefits of steroids without the side affects if your mate is dead keen on suppliments.