With the increasing prevalence of chronic non-communicable diseases, excessive sugar intake has been recognized as a major contributing factor to health problems such as obesity, diabetes, and cardiovascular diseases. Consequently, sugar reduction has become an important direction in food processing. To develop food structural systems with sugar-reduction potential while enhancing sweetness perception, a structured lipid system based on capillary action was constructed using resistant dextrin–sucrose/water/sunflower oil (RD-SUC/W/SFO), and its potential application for sugar reduction in flavored filling creams was investigated. By regulating the water content, rheological measurements, oil-binding capacity analysis, and microscopic observations were conducted to systematically evaluate the effects of moisture levels on the microstructure, network strength, and thixotropic recovery behavior of the structured lipid system. The structured lipid was further incorporated into a strawberry milk-flavored filling cream, and its sugar-reduction performance as well as sensory quality were assessed through sensory evaluation. The results indicated that when the water content was 0.75‰, the structured lipid exhibited optimal structural stability, with an oil-binding capacity of 83.11% and a yield stress of 21.65 Pa, along with a high thixotropic recovery rate of 92.58%. Application in flavored filling cream demonstrated that the structured lipid significantly enhanced sweetness perception, enabling more than 20% sugar reduction while maintaining no significant differences in texture and mouthfeel compared with the control group (P>0.05). In conclusion, an RD-SUC/W/SFO structured lipid system was successfully developed, and its potential application for sugar reduction in flavored filling creams was demonstrated. This study provides a novel strategy and technical approach for the development of reduced-sugar food products.