Judo, but I think Hawaii is the only state with HS Judo.
No other sports will translate directly to MM/grappling. However, I think two common ones can help alot. One is football, the sport itself has jack shit to do with fighting (other than the player learns to be assertively aggressive, and this is only for some positions) but alot of HS football teams S&C their players religiously, so he gets 4 free years of plyometrics/explosion/strength training. The other, though I never played, is Soccer. Soccer has ALOT of running, and not jogging, but constant start and stop running, and every former soccer player I ever knew who took up fighting, had decent leg/hip power and could kick decent out of the gate. This in addition to being conditioned mentally to run all the time (so roadwork isnt such a chore) is an asset IMO.
Any sport is decent though, as one develops physically no matter what, and give a future physical base to grow from, but the only practical application sports will be Wrestling, and Judo.