Assess and compare lifecycle environmental impacts of single-use plastic (PET) bottles versus reusable water bottles (stainless steel, aluminum, reusable plastic) across production, transport, use (including washing), and end-of-life stages; for given usage scenarios (daily commuter, occasional user, athlete, school) calculate break-even reuse counts using stated or reasonable assumptions, evaluate trade-offs (GHG emissions, water use, waste, recycling rates, microplastic risk), and recommend the best option with clear justification and cited assumptions.