The device for extemporaneously preparing a hot beverage anywhere and anytime from a soluble powder comprises a container which is divided into an upper hollow space and a lower hollow space by a baffle. The lower hollow space contains a quantity of drinkable liquid and the upper hollow space a quantity of soluble powder able to produce said beverage. An elongated hollow element is provided, which is open at its two ends and which connects the lower and the upper hollow spaces, sealing membranes are provided for sealing the connection between the upper and the lower hollow spaces through the elongated element. The sealing membranes can be made ineffective by intervention of the user or once a predetermined pressure inside the liquid has been reached.
