TL;DR
The comic-book super-soldier was built in a single lab with a single serum. The real one, if it ever arrives, is being assembled piece by piece in separate labs. The boldest piece is DARPA's RESTORE program, which is trying brain stimulation to make about three hours of sleep do the work of a full night for warfighters. Elsewhere, a drug has halved the muscle people lose on weight-loss shots, brain implants have set new speed records, and powered suits are on sale for walking help. If those lines ever meet, a soldier could need far less sleep and keep strength through deprivation. Today, none of them has been combined, RESTORE has published nothing, and the best-proven performance booster in the Army is not a drug or a device at all. It is coaches and physical therapists.
Below the line, for paid subscribers: The full story: where it stands, how we got here and what's dated next; our Odds board on 5 milestones, starting with "DARPA's RESTORE sleep program publishes results by 2028"; our labeled speculation on what it adds up to; and every source.