Water

Yes, if it was safe to drink before boiling. Reboiling does not make it unsafe, though repeated boiling can concentrate minerals slightly as water evaporates.

Keep it in a clean, tightly covered container, away from sunlight and heat. Once you have poured from a bottle, refrigerate it if you want to keep it cool and use it promptly.

Water itself does not spoil like food, but its taste can change during long storage, especially if the bottle is kept warm or in sunlight. Keep sealed bottles cool and out of direct light.

Use cold tap water for cooking, then heat it in the kettle or pan. Hot water can pick up more metals from household plumbing while it is sitting or flowing through pipes.

Yes, but its bubbles and slight acidity can affect the result. It works well in light batters such as tempura, while still water is the better choice when you want a neutral flavour.

Chill it in a covered jug; cold water often tastes less noticeable. You can also add a slice of lemon or cucumber just before serving.