Glucose intake has been found to improve some aspects of cognitive performance; however, results are often inconsistent. This inconsistency may be related to expectations surrounding glucose, which can have strong effects on performance outcomes. The present study evaluated the independent and interactive effects of acute sugar intake, in the form of high-fructose corn syrup (HFCS), and sugar expectancies on cognitive performance and mood. One hundred five healthy young adults were randomized according to sugar intake and expectation: consumed-sugar/told-sugar, consumed-sugar/told-no-sugar, consumed-no-sugar/told-sugar, and consumed-no-sugar/told-no-sugar. Thirty minutes after sugar or no-sugar intake, participants completed the Profile of Mood States and a battery of cognitive tests, including immediate and delayed recall, the Stroop test, n-back task, and continuous performance task. Tension increased following the expectation of consuming sugar, regardless of sugar consumption (p < .05). On the continuous performance task, accuracy and sensitivity were higher (ps < .05) and false alarm rate was lower (p < .05) following sugar than no sugar intake. No effects of sugar intake or expectation were found for any other mood or cognitive measure (ps > .05). The findings suggest that sugar intake in the form of HFCS may benefit certain cognitive processes, such as those that require sustained attention, but that the expectation of sugar intake is not sufficient to produce such benefits.