According to the Department of State website, you will need a M-1 visa. Indeed, it sounds like your training matches the following description:
Vocational or other recognized nonacademic institution, other than a language training program
Note that if it is your main purpose of travel, the VWP program is not the right choice. The B visa might or might not be the right choice, the website is unclear (and @Dennis comment shows it might be the right choice):
Citizens of Visa Waiver Program (VWP) participating countries who intend to study cannot travel on the VWP or on visitor (B) visas, except to undertake recreational study as part of a tourist visit.
Enrollment in a short recreational course of study, which is not for credit toward a degree or academic certificate, is permitted on a visitor (B) visa.