A dosing apparatus for dosing a powder product inside containers includes a hopper provided with an inner cavity for containing the product, a lower portion provided with a supply duct with a terminal aperture for the outflow of the product, a metering screw rotating inside the supply duct and a washing manifold provided with an inlet opening and containing at least a sonotrode. In a cleaning configuration of the dosing apparatus, the washing manifold is connected to the hopper coupling the inlet opening to the supply duct, so as to receive and contain a washing liquid introduced in the hopper. The sonotrode is activated to produce alternate pressure waves capable of generating in the washing liquid air bubbles adapted to propagate towards the inner cavity through the supply duct, and to implode thus creating shock waves.