tell him to work construction, framing,demolition,deconstruction,concrete etc i know its a little wierd but, theres something about swinging a hammer,using a screwgun,hammerdrill,crowbaring shit,using a grinder,mixing concrete that'll really straighten a drummer out, has for me, speed and endurance,that is.

this goes along with doing the above mentioned advice

i once had the rare opportunnity to help friends who do metalwork art, blacksmithing, id roll in and sledge rebar all day,listen to old metallica,drink a pot of coffee, that was the most intense work in my life, my drumming greatly improved

if your friend is in high school, whatnot, construction companys are more willing to hire you, make good money too