Plastic containers may cause a toxic chemical reaction with the water, especially when exposed to sunlight. We use exercise to get oxygen into the body and get the oxygen to circulate through the blood so that it can carry nutrition to the cells. Walking, running, stretching, deep breathing exercises and nearly every active sport get more oxygen into the body. This energy is used to build new cells and to clean the body of toxins such as dead fuel, waste, toxic chemicals, viruses and radiation. For the fuel and oxygen to get to the cells, they must be carried throughout the entire body by the blood.
Physical activity gets the blood moving throughout the body.
The byproduct of burning fuel is waste material, like smoke and ash. Often the fuel itself IS waste material as far as the engine in concerned. You don't because the engine treats it as waste. It won't burn and so must be eliminated. Too much waste clogs up the engine and it stops running.