Water does not go bad by it self. In a closed container:
- The container material might leach in to water (plastics)
- The water might not have been clean at the start and germs might multiply or other things start to grow, especially with sun light.

Heat might cause issues with plastic bottles and what they release in the water.

Freezing temperature wil cause issues due to explanding.

Rotating some bottles of water seems to be most succesfull to me. Plastic seems to have enough expantion space. Store in the trunk where it's shaded from the heat. In winter i toss it in a cooler to reduce the temperature swings and act as a catch for any leakage.