In this study, we demonstrate a simple and low cost method to synthesize N/P/K co-doped porous carbon microfibers (CMFs) from a sugar-rich byproduct (cane molasses) as the precursor material. A two-step method for the synthesis of N/P/K co-doped porous CMFs involving electrospinning of precursor material followed by simple carbonization at various temperatures (773.15–1173.15 K) was successfully applied. The N/P/K co-doped porous CMFs exhibited high specific surface area (∼580 m² g⁻¹) and hierarchical porous structure. The potential application of N/P/K co-doped porous CMFs as supercapacitor electrodes was investigated in a two-electrode configuration employing aqueous K₂SO₄ solution and ionic liquids/acetonitrile (ILs/ACN) mixtures as the electrolytes. A series of electrochemical measurements include cyclic voltammetry, galvanostatic charge–discharge and cycling durability all confirmed that the CMF-1073.15 supercapacitor exhibited good electrochemical performance with a specific capacitance of 171.8 F g⁻¹ at a current load of 1 A g⁻¹ measured in 1.5 M tetraethylammonium tetrafluoroborate (TEABF₄)/ACN electrolyte, which can be charged and discharged up to a cell potential of 3.0 V. The specific energy density and power density of 53.7 W h kg⁻¹ and 0.84 kW kg⁻¹ were achieved. Furthermore, the CMF-1073.15 supercapacitor showed excellent cycling performance with capacitance retention of nearly 91% after 2500 charge–discharge cycles, characterizing its electrochemical robustness and stable capacitive performance.