<p>Achieving fire protection in rigid polyurethane foams using non-halogenated fire retardants presents a significant challenge. Consequently, there is an ongoing quest for new, environmentally friendly materials that can effectively diminish the flammability of porous polyurethane composites. This article presents research findings on a novel synergistic system composed of sucrose and expandable vermiculite, which serves as an excellent alternative to traditional flame retardant polyurethane foams, while also addressing ecological concerns. A comprehensive set of experimental techniques was employed in this study. The foams’ morphology, apparent density, mechanical properties, dimensional stability, surface wettability, and water absorption were determined. Additionally, thermogravimetric analysis (TGA) was used to investigate the thermal stability of the composites, and cone calorimetry was used to assess flammability parameters, including heat release and smoke production. Together, these techniques enabled a detailed characterization of the structural, mechanical, and fire-retardant properties of rigid polyurethane foams modified with sucrose and vermiculite. The study demonstrated that incorporating this fire retardant system led to a marked reduction in both the average heat release and the amount of smoke generated during foam combustion. Additionally, the sucrose/vermiculite system enhanced several functional properties, including mechanical strength. The modified foams exhibited improved resistance to bending and compression, along with increased density and hardness. These improvements can be attributed to a relatively homogeneous structure that was further reinforced by the presence of sucrose crystals.</p>