[Svartalfiar]

I have long advocated for inexpensive pre-basic training camps, with the idea to get them in shape and physically fit *before* basic training. All you need is about 1 square mile, divided by flat and paved hills of several grades.

The National Guard already has something like this. Once you enlist, you're placed in an RSP unit that you do monthly drills with until you leave for basic. Start learning ranks, Creed, Army song, and do PT at least two days a month. Gives kids a much better start on basic than active duty recruits.
Recruit Sustainment Program.

[yefragetuwrabrumuy]

Not quite what I was looking for. What I would target are those that are 20-50 pounds overweight, who have never exercised, and are generally borderline for health because of it. Smokers, drinkers, “otaku”-types who have spent years playing games on computers.

These are far more common among civilians. A pre-camp would go for a complete health rebuild. This is why they are all on individualized diets and six days a week exercise under supervision.

It could even have goal rewards for meeting and exceeding standards.

Once again, the higher this can raise the average for basic camp, the better their training there can be. And the cost to the military would be peanuts compared to about anything else.