Focusing on the defect that existing literature does not explicitly model B2C sharing businesses as time-sharing rentals, this paper introduces the efficiency of sharing service operations (ESSO) that captures the turnover rate of the shared product in serving consumers, and develops and solves the corresponding two-stage game-theoretic model where a manufacturer chooses its operational strategies among the traditional sale, internal B2C sharing business extension, and external B2C sharing business extension in stage 1. In stage 2 the manufacturer and a third-party B2C sharing platform (when the external B2C sharing business extension is chosen) make their concrete operational decisions. With the subgame perfect equilibrium, we obtain the following main results. (1) The necessary condition under which the manufacturer chooses the internal (external) B2C sharing business extension is that the ESSO of the manufacturer (the third-party B2C sharing platform) goes beyond a threshold, and given that this necessary condition is satisfied, the manufacturer chooses the external B2C sharing business extension if and only if the ESSO of the third-party B2C sharing platform is high enough (relative to the ESSO of the manufacturer) and the manufacturer’s ESSO is not at a very high level, otherwise it chooses the internal B2C sharing business extension. (2) If the third-party B2C sharing platform is captured via its ESSO and ability to meet sharing demand, not only does Result (1) still hold qualitatively for an arbitrarily given level of the ability to meet sharing demand, but also a substitutive relationship between these two dimensions exists in the sense of their impacts on the manufacturer’s choice of the internal B2C sharing business extension. (3) From stakeholders’ perspectives, for an arbitrarily given level of the ESSO of the manufacturer, the optimal choice of its operational strategy is three-win for the manufacturer itself, consumers and the social planner if and only if the ESSO of the third-party B2C sharing platform is either high enough or low enough, otherwise it leads to some loss of either consumer surplus or social welfare.