Bottle having internal mixing compartment

A method of mixing a powder and a liquid within a portable drinking bottle comprising the steps of:

• a) providing:
• a portable drinking bottle defined by a sidewall extending from a base to a top, an opening in the top, and a removable upper lid sealing the opening;
• an internal mixing compartment defined by a cylindrical, rigid screen mesh sidewall extending into the bottle from the base of the bottle to a mixing compartment top, the internal mixing compartment having a cross-sectional area less than the cross-sectional area of the bottle;
• an opening to the mixing compartment in the base of the bottle;
• a removable bottom lid sealing the opening to the mixing compartment in the base of the bottle;
• and,
• at least one agitator in the mixing compartment;
• b) adding a particulate material into the internal mixing compartment by inverting the drinking bottle, removing the bottom lid and pouring the particulate matter into the mixing compartment chamber, and resealing the bottom lid;
• c) adding a liquid to the bottle;
• and,
• d) manually vigorously shaking the bottle.