Consuming a glucose beverage between tasks requiring willpower maintained or increased participants' willpower levels compared to those who consumed an artificially flavored drink or water.

“when subjects are given glucose in between a first hard task that required willpower and a second hard task that required willpower and in some experiments a third hard task that required willpower that their levels of willpower were maintained consistently from one task to the next and in some cases increased from one task to the next if they had more glucose available because they drank this glucose drink”