Low-rank coals (LRC), encompassing lignite and sub-bituminous categories, constitute a substantial global energy reservoir; however, their utilization in unprocessed form is hindered by excessive moisture content, diminished calorific value, and augmented emissions during combustion processes. The enhancement of these coals through various heating media are hot water, hot oil, and steam—can markedly improve their quality by diminishing moisture levels and augmenting energy density. This comprehensive review investigates the influences and efficacies of these disparate heating media on the properties of LRC, concentrating on the operational mechanisms of each method, their effects on coal characteristics, and their practical applications within industrial contexts. Hot water drying predominantly employs hydrothermal treatment to achieve moisture reductions of up to 50%, thereby enhancing the thermal stability of the coal, whereas hot oil drying facilitates more vigorous heat transfer, lowering moisture content to beneath 15% and optimizing energy density in a cost-effective manner. Steam drying, frequently implemented in large-scale power generation facilities, improves both moisture elimination and calorific value by as much as 2,000 kcal/kg, rendering it particularly suitable for high-demand energy applications. In contrast, each method reveals unique environmental and economic ramifications, with steam and hot oil drying exhibiting significant potential for efficiency when synergistically integrated with waste heat recovery systems. The results suggest that the selection of the most suitable drying technique is contingent upon resource availability, economic factors, and the specific requirements of the application. Ultimately, the optimization of these heating media for the upgrading of LRC has the potential to enhance its viability as a cleaner and more efficient fuel source, thereby contributing to the advancement of sustainable energy initiatives.