When I was in college -- which seems ages ago now -- I wasn't a music major (silly me; 20-20 hindsight) and had the usual college problems; not quite the same as a full time job, but not wholly unlike in terms of the end of the day feeling. I used to practice very late at night -- say 11:00 PM or so -- for a couple of hours. I had the use of the big chapel organ (I was an organ student) then, rather than one of the practice organs, which was great, and no one bothered me at all. In later years, when I had a full time job and was also a church organist (before I got a full time job as that!) again I used to come home, have dinner, see the kids to bed -- and go out and practice late at night.
It usually took me half an hour or so to really get into it before the practicing started to become effective, but once I did it was excellent, as there was a feeling of me and the music and the instrument and nothing else to worry about.
For myself, at least, I can't recommend drugs or stimulants -- even coffee -- although I did then, and do now, smoke which helps my concentration (but I don't recommend smoking! It really isn't all that good for you...)