Where can I get the best online barista training?

The job of "barista" is a skill type occupation, requiring not only knowledge but also physical abilities. There probably is no "online" site where you can get training in this area, and even if there were one, it is unlikely that anyone would hire you with nothing more than that type of background. If you are serious about working in a place where fancy coffee beverages are made and served, your best bet is to inquire personally about the kinds of experience they want from the people they hire. Visit one or two, speak to the manager, and ask how you can get the necessary preparation to qualify you for a job. They'll be glad to tell you.

Starbucks.