Selective hydrolysis of cellulose into glucose is a critical step for producing value-added chemicals and materials from lignocellulosic biomass. In this study, we found that co-impregnation of crystalline cellulose with sulfuric acid and glucose can greatly reduce the time needed for ball milling compared with adding acid alone. The enhanced reaction time coincides with the rapid formation of branched α(1→6) glycosidic bonds, which have been shown to increase water solubility of β(1→4) glucan oligomers. Co-impregnation of glucose was crucial for the rapid formation of the α(1→6) branches, after which a carbon-based catalyst can rapidly hydrolyze the water-soluble glucan oligomers to 91.2% glucose yield faster than conventional approaches.