This study investigates two key aspects of sand concretes: (1) the impact of constituent types—silica sand and crushed sand—on their physico-mechanical properties, and (2) the influence of plant fiber reinforcement (DISS fibers) at varying percentages on their mechanical and thermal performance. To achieve these objectives, a systematic experimental approach was adopted. Initially, sand concretes with varying proportions of silica sand and crushed sand were developed to determine the optimal formulation. Subsequently, the best-performing formulation was reinforced with DISS fibers at different dosages. The results revealed distinct workability characteristics based on the sand type. Silica sand-based sand concretes exhibited firm workability, while those made with crushed sand were highly fluid. Balanced formulation comprising 50% silica sand and 50% crushed sand provided optimal plastic workability. In terms of mechanical performance, all sand concrete formulations demonstrated superior tensile strength compared to traditional concretes, with the 50%-50% formulation exhibiting the highest mechanical performance. Moreover, the inclusion of DISS fibers significantly enhanced the thermal properties of sand concretes, reducing thermal conductivity and effusivity as the fiber content increased. These findings underscore the potential of hybrid sand formulations and plant fiber reinforcement to improve the performance and sustainability of sand concretes.