The aim of this study was to analyse the impact of tasting temperature on difference thresholds of aqueous solutions of sucrose, glucose and fructose. By using the forced-choice constant stimulus procedure, reference concentrations of 2 g/100 g and 5 g/100 g sucrose, and glucose and fructose solutions iso-sweet to 5 g/100 g sucrose were evaluated at 5 °C, 22 °C and 56 °C. Depending on reference concentration, Weber fractions for sucrose range from 0.07 to 0.09, and those for glucose and fructose from 0.05 to 0.08 and 0.04–0.07, respectively. Significantly higher Weber fractions were recorded at 56 °C, indicating that higher sample temperature reduces sensory sensitivity towards sweetness. This may be important for the development of sugar-reduced instant beverages.