Sherlock’s Military Kink is Canon!
In A Study in Pink when Sherlock introduces John to 221B he has a copy of Eagle: Adventure Survival Truth Magazine in the boxes with his trunk.
EDIT -> Professorfonz figured out the magazine was Eagle and found an earlier issue of it. (I tracked down Sherlock’s issue.) On behalf of her amazingness, you’re welcome!
EDIT -> Tween!Sherlock. This magazine appears to have run in the 1980’s only so they’re probably from Sherlock’s youth which makes sense given that they’re with what I’m claiming is the boarding school trunk.
Trunk Photo from Arwel Wyn Jones’s 221b set panorama.
EDIT -> Sherlock’s is the June, 1983 issue of Eagle Adventure Survival Truth Magazine. Headlines include: “Street Fighting Techniques,” “L.A.W. Update,” “82nd Airborn,” etc. I’m looking for a better photo of the issue.