This chapter examines the contested narratives of sustainability at Barongan Market, a temporal marketplace in peri-urban East Java, Indonesia. While publicly promoted as eco-conscious placemaking initiatives, its everyday material practices—such as the re-emergence of plastics and reliance on non-local ‘natural’ packaging—reveal a disconnection between symbolic sustainability and ecological realities. Drawing on Materiality and Assemblage Theory, this chapter conceptualises materials like bamboo, banana leaves, paper, and plastic not as passive objects but as active agents shaping economic behaviour, ecological discourse, and community adaptation. Based on ethnographic fieldwork, the findings suggest that sustainability at Barongan Market is often commodified, shaped more by aesthetic branding and economic pressure than by systemic ecological transformation. The chapter contributes to debates on temporal placemaking in the Global South context by showing how sustainability is performed, negotiated, and often contradicted through material paradoxes inherent in its assemblage. It calls for place-sensitive planning and design that moves beyond green branding towards grounded accountability and support for local material ecosystems.