Hardly soluble beverage product

A hardly soluble beverage product, comprising:

• a container comprising a main body that contains a content and that has a container mouth as an outlet of the content, and a cap that is mounted on the container mouth to close the main body,
• wherein the main body can be closed again by mounting the cap on the container mouth, after dismounting the cap from the container mouth,
• the content includes hardly soluble powder material that is dissolved in a predetermined liquid or mixed with the predetermined liquid to be drunk, and
• an internal volume of the container is set to a total of:
• a volume corresponding to a volume of the powder material contained in the container;
• a volume corresponding to an amount of the liquid determined in accordance with an amount of the powder material to be mixed or dissolved with the liquid;
• and a volume as an extra space to cause turbulence of the powder material and the liquid.