You can clean and sharpen a coffee grinder with rice. First, grind up some rice in the coffee grinder to remove any coffee residue. Next, unplug the grinder and disassemble it. Clean all of the parts with soapy water and a brush. Rinse well and dry completely. To sharpen the blades, grind up some rice in the grinder until they are sharpened to your desired level. Reassemble the grinder and enjoy your freshly ground coffee!