Last few decades, unwanted climate change and global warming have forced us to think about the world environment. This paper investigates a perishable supply chain system consisting of one manufacturer, one third-party logistics service provider, and multiple retailers. The logistics provider and retailers use cooling technologies to maintain the product's freshness. Here, consumers' demand is evaluated from the utility function based on price, freshness, and sustainability level. The environmental impacts of the system are measured from the amount of energy consumption and carbon emission. Also, the supply chain members are taking their decisions in cooperation, non-cooperation, and coordination decision scenarios to maximise their profit and reduce total environmental impacts. We develop a general model and a particular model under different decision scenarios. The optimal sustainability level, price, and freshness-keeping-effort (FKE) are derived using the Stackelberg game theory. A numerical experiment as well as sensitivity analyses of various important parameters are conducted. It explores that (i) FKEs have more impact than the sustainability level for the consumption of perishable products. (ii) The retailer-leadership scenario is the most effective for reducing carbon emissions and energy consumption whereas the cooperative decision scenario is better for maintaining the freshness level.