Thermal cracking of sugars for production of glycolaldehyde, a potential renewable platform molecule, in yields up to 74% with up to 95% carbon recovered in the condensed product was demonstrated using glucose as the feed. The process involves spraying an aqueous sugar solution into a fluidized bed of glass beads. Continuous operation was shown for more than 90 hours with complete conversion and stable product selectivity. Besides glycolaldehyde, the other identified condensed products were pyruvaldehyde (9%), formaldehyde (7%), glyoxal (2%), acetol (2%) and acetic acid (1%). The effects of temperature, glucose feed concentration and type of sugar feedstock were investigated. Cracking the monosaccharides fructose and xylose showed very different product distributions from glucose, but similar carbon recovery. A reaction network in agreement with the main observed products from cracking of monosaccharide sugars is suggested.