Adding small amounts of different carbonaceous additives during the production of foundry coke can improve its mechanical, physical, and chemical properties. Industrial tests in Western Siberia and the Urals showed that using coke dust, oil-coke fines, semi-coke fines, and rubber crumb as additives can enhance the quality of foundry coke. By adding coke dust from a dry quenching facility, the coarseness and strength of foundry coke increased. Adding oil-coke fines improved the strength of foundry coke and reduced ash content. Using modified oil coke as an additive can further enhance the quality of foundry and blast furnace coke. Additionally, replacing some coal with semi-coke fines in the production burden led to improved coke quality. These findings demonstrate effective methods for improving the quality of foundry and metallurgical coke.