A beverage dispensing system comprises a container, an attachment mechanism, and a cartridge. The container may hold a mixing solution or liquid, such as water, to be mixed with the contents of the cartridge. The attachment mechanism is generally located within the container. The attachment mechanism may comprise an engagement assembly, a piercing portion, and a valve assembly. The engagement assembly may generally receive the cartridge within the attachment mechanism. The piercing portion may generally pierce the cartridge, thereby releasing the contents of the cartridge into the container. The valve assembly may generally open upon engagement of the cartridge with the attachment mechanism. The cartridge generally engages with the attachment mechanism to open the cartridge to be dispensed into the container, thereby combining the contents of the cartridge with the liquid within the container to create a drinkable beverage.