Is the penitent still indebted to the owners of taverns and nightclubs to whom he did not pay for the alcohol he consumed, and is he required to return the money to them?

You do not owe anything to the owners of taverns, because alcohol is not considered wealth and has no value. It is like blood, carrion, and other impurities. The Messenger of Allah, peace and blessings be upon him, forbade its sale and commanded that it be poured out. Therefore, that which is not permissible to sell and cannot be owned holds no guarantee.