When the Prophet (may Allah's peace and blessings be upon him) got up at night, he would cleanse his mouth with Siwak (tooth-stick)

The Hadīth affirms that using the Siwāk is prescribed under the Shariah after sleeping at night, as sleep entails a change to the odor of the mouth and the Siwāk is a means of cleaning.
It emphasizes that using the Siwāk is prescribed under the Shariah whenever the mouth has a foul smell, based on the above meaning.
Cleanliness in general is prescribed under the Shariah and it is part of the Sunnah of the Prophet (may Allah's peace and blessings be upon him) and one of the sublime etiquettes.
The Siwāk is used for the whole mouth, including the teeth, the gums, and the tongue.
The Siwāk is a stick cut from the Arak tree or other trees. It is used to clean the mouth and teeth, freshen the mouth, and remove bad odors.