Is it permissible, Islamically, to add two days to my salary to give to the company's cleaning staff to help them?

This action is not permissible because it involves deception and fraud against the company. The Messenger of Allah, peace and blessings be upon him, said: "Whoever deceives us is not of us," and "Cunning and deceit are in the Fire." The good intention of consoling the sanitation workers does not justify the corrupt means, because Allah is good and accepts only what is good.