Thermos flask can hold coffee, but it should be noted that thermos flask can't hold coffee for a long time, otherwise it will affect the taste of coffee and make it difficult to clean thermos flask. Putting coffee in a thermos cup will affect the taste, and if the thermos cup soaked with coffee is not cleaned in time, it may cause pigment residue, which is difficult to clean. However, you can't make coffee in a thermos cup because the stainless steel in the thermos cup contains metal elements. In acidic environment, some substances that will react with metals and are harmful to the health may be dissolved out, which will affect the life and health of the cup. Therefore, it is recommended not to make coffee in a thermos cup. Usually, products such as plastic or glass ceramics can be used to make coffee. Thermos flask can hold coffee, but it should be noted that thermos flask can't hold coffee for a long time, otherwise it will affect the taste of coffee and make it difficult to clean thermos flask. Putting coffee in a thermos cup will affect the taste, and if the thermos cup soaked with coffee is not cleaned in time, it may cause pigment residue, which is difficult to clean. However, you can't make coffee in a thermos cup because the stainless steel in the thermos cup contains metal elements. In acidic environment, some substances that will react with metals and are harmful to the health may be dissolved out, which will affect the life and health of the cup. Therefore, it is recommended not to make coffee in a thermos cup. Usually, products such as plastic or glass ceramics can be used to make coffee. You can't put the thermos in the coffee. Because the material of the coffee mug may react chemically with the substances in the coffee, and the coffee will affect the taste after being put into the mug. In addition, the color of coffee is darker. If the mug soaked in coffee is not cleaned in time, it may cause pigment residue and it is difficult to clean it. There are many shapes of mugs now, and some strange shapes are even more difficult to clean, so coffee can't be put in mugs.