There are many companies that all claim to manufacture or sell Hydrogen Water Machines. Be aware that in many cases they are nothing more than an Alkaline Water machine that may create H2 as a byproduct of changing pH to an alkaline state but will need to be striped and cleaned every two weeks to ensure optimal hydrogen production. If it creates molecular hydrogen through a Proton Exchange Membrane (PEM) then you are most likely safe.
Even in this regard, it is wise to be aware that many products that claim to operate via PEM aren't always the best quality. In many cases, they have been found to leak onto your counter tops leaving you with severe kitchen damage, electrical issues in the machine, and a gross lack of good filtration.
When shopping for a Hydrogen Water Machine, you will want to look for a good warranty, long track record in the industry, and are they a multi level marketing company or not. If you enjoy being apart of a Multi Level Marketing/Direct Sales Company to be able to buy a Hydrogen Water Machine, then there are several companies out there. But there are also other direct ecommerce companies in the industry that sell directly to you. Know before you buy.
Do they have robust filtration that will filter toxins like chlorine, fluoride, pharmaceuticals, pesticides, and heavy metals. In this day and age, this is absolutely crucial. There are very few companies that offer built in filtration of the proper caliber in the product. Most offer pre-filtration at an added cost. Know before you buy.