<p>In this paper, a sustainable economic production quantity (EPQ) inventory model for seasonal products is developed with a particular focus on the ice cream industry. A multi-phase demand function is considered to capture the variations in demand across different seasons. The proposed model incorporates preservation technology, green investment, and eco-friendly packaging to effectively address the environmental and economic challenges of the ice cream production process. Three models are developed and compared: preservation technology investment only (Model 1), preservation technology combined with green investment (Model 2), and preservation technology combined with green investment, and eco-friendly packaging (Model 3). Two variants of particle swarm optimization (PSO) namely weighted PSO (WPSO) and constriction PSO (CPSO) are employed to find the optimal solution for the models, with a focus on minimizing total costs while enhancing sustainability. The results highlight that the integration of green investment significantly reduces carbon emissions. Although green investment and eco-friendly packaging costs slightly increase overall costs, the increment is moderate and manageable, thus providing a pathway for sustainable production. The proposed model provides valuable insights for managers in the ice cream industry and other sectors dealing with seasonal demand, helping them balance cost-efficiency and sustainability.</p>