The recycling of waste plastic to useful advanced nanomaterials has played a lucrative impact on our ecosystem. The present work represents the reliable means to transmute the plastic waste into highly luminescent carbon dots (CDs) having quantum yield of 59%. The formed particles have possessed a strong fluorescence emission peak at 660 nm and an absorption peak at 270 nm. The developed particles were found to be highly stable towards variability in reaction medium. Furthermore, various characterization techniques were accomplished to scrutinize the physical and chemical properties of obtained CDs. The strong optical and emission characteristics with high surface to volume ratio of CDs have been explored in developing highly efficient “turn-off” fluorescence sensor for sulphite anion in aqueous media with limit of detection of 0.34 μm under optimal conditions. The practical utilities of developed CDs have been explored over different ranges of water sources. The outcomes of current work endowed a simple, rapid, benign and remunerative sensory probe for the detection of the sulphite ions from the wasted plastics for environmental remediation.