Will a person who eats, drinks, and clothes himself from ill-gotten gains and knows that his supplication is not answered be sinful if he supplicates to Allah to change his situation and suffice him with His lawful instead of His unlawful, because he does not find the strength to change his food, drink, and clothing?

The possessor of unlawful wealth is not forbidden from supplicating, nor is he prohibited from it. However, his supplication is likely to go unanswered. Nevertheless, it is not definitively certain that it will not be answered. Allah may graciously choose to answer him, and Allah may even answer the supplication of a disbeliever. Therefore, there is no basis for deeming the possessor of unlawful wealth sinful for supplicating.