2. Among all the cups made of materials, the glass is the healthiest. This kind of glass contains no organic chemicals in the firing process. When people drink water or other drinks from glasses, they don't have to worry about chemicals being drunk into their stomachs. Moreover, the glass surface is smooth and easy to clean, and bacteria and dirt are not easy to breed on the glass wall. Therefore, it is the healthiest and safest for people to drink the water in the glass. In addition, experts also advocate the use of enamel cups, because enamel cups are made of thousands of degrees of high-temperature enamel and do not contain harmful substances such as lead, so they can be used with confidence.