This study investigated sweet–sour taste interactions in novel sweeteners using a 3 × 2 factorial design consisting of Sweetening System (three levels: sucrose; d-allulose; and a blend of d-allulose and Monk fruit extract) and Acidity (two levels: with or without citric acid). 110 untrained Chinese subjects participated using the temporal check-all-that-apply (TCATA) method. Mixed-model ANOVA was conducted to investigate the effect of Sweetening System, Acidity, and their interactions on the fractional Area Under the Curve within three 20 s time intervals (attack, evolution, finish). Treatments were compared using Dunnett's test with sucrose as control. Citric acid suppressed the sweet taste of both sucrose and d-allulose more than the blend of d-allulose and Monk fruit extract throughout attack and evolution time intervals. This finding was confirmed by a significant interaction between Sweetening System and Acidity for sweet taste. Sour taste was not affected differently by different Sweetening Systems or the difference in sweetener concentration.