Rice milk is a grain milk made from rice. It is mostly made from brown rice and commonly unsweetened. The sweetness in most rice milk varieties is generated by a natural enzymatic process, cleaving the carbohydrates into sugars, especially glucose, similar to the Japanese amazake.ommercial brands of rice milk are often fortified with vitamins and minerals, including calcium, vitamin B12, vitamin B3, and iron. Rice milk is often consumed by people who are lactose intolerant, allergic to soy or have PKU.