In general, preference for different sugars in nectarivores and frugivores is related to the composition of their food. We determined individual preferences in Cynopterus brachyotis and Pteropus rodricensis, and group preferences in one group of P. rodricensis and two mixed groups of P. rodricensis, P. pumilus, P. vampyrus, and P. hypomelanus. Most bats were born in captivity and received a diet with a composition of sugars of sucrose = glucose > fructose during 1 to 6 years before the experiment. We tested the hypothesis that diet composition influences food preferences, and predicted that bats would not discriminate between sucrose and glucose, and would prefer sucrose and glucose over fructose. Individuals and groups consistently favored sucrose over glucose and fructose, and fructose over glucose. We also determined gustatory thresholds for (0.15 % weight/weight) than fructose (> 0.5 %) and glucose (0.5 %). Food preferences, in general, did not match the composition of the diet. Gustatory thresholds may be a valid proximate reason to explain preference for sucrose over glucose and fructose, but not for preference for fructose over glucose.