<p>One of the major concerns facing the construction sector is the severe environmental and financial implications of producing ordinary red-clay bricks, which include topsoil degradation, greenhouse gas emissions, energy use, and higher expenses. This study develops and tests Bottle-Encapsulated Sludge Bricks (BESB), in which dewatered sewage sludge is stabilised with lime and compacted inside discarded PET beverage bottles that act as a stay-in-place formwork. Although previous studies have investigated different waste materials as fillers for plastic bottles, sewage sludge has not been fully discussed before, and owing to the variance in sewage treatment processes, direct comparison across these studies is difficult. This study proposes an innovative reuse of sludge-filled plastic bottles as an alternative to traditional bricks. By optimizing water content (5%) to achieve 18.16 N/mm² compressive strength surpassing conventional red clay bricks (17 N/mm²) the work demonstrates a low-cost, environmentally friendly solution for waste repurposing and sustainable construction. The approach used in this research entails obtaining and preparing Polyethylene Terephthalate (PET) bottles and sewage sludge, as well as executing a series of tests to determine the appropriate water content and strength capabilities. The performance of the sludge-filled bottles was examined using compressive strength and the test of exposure to salt. According to the data, the sample with 5% water content has the best compressive strength, demonstrating its potential in construction sector. The plastic bottles filled with sewage sludge might solve the environmental difficulties linked to the typical production of traditional building bricks as well as provide a cheaper and sustainable means of construction, particularly in developing countries. It effectively handles the dual concerns of eliminating plastic waste and controlling sludge disposal in order to encourage more sustainable housing for all.</p>