Ultrathin carbon nanosheets were fabricated using renewable carbon sources. Cellulose, an important component in the food industry, was processed to form a food byproduct and used to synthesize carbon nanosheets. Both bacterial and nonbacterial cellulose from kombucha byproducts and apple pomace, respectively, were processed via purification and pyrolysis. An inert argon atmosphere and elevated temperatures of 600 °C–800 °C for 20 min were maintained during pyrolysis. Under these conditions, the apple pomace produced a higher yield of nanosheets than the kombucha byproduct. The nanosheets with the thickness of 4 nm were characterized using different spectroscopic techniques such as Fourier transform infrared spectroscopy and Raman spectroscopy as well as microscopic techniques such as scanning electron microscopy and atomic force microscopy. This sustainable, simple, and green method of carbon nanosheet production is a promising alternative to conventional methods of production.