Here’s my pro tip, been doing it for a few months when it’s hot:
Put a bottle of water in the freezer, and another 2 in the fridge overnight ( like a 1.5 litre Evian or Buxton or whatever)
Then, in the morning take all 3 (2 cold and 1 frozen).
For the first hour, drink one of the cold ones. By about 11am, about 25% of the frozen bottle will have melted, drink this ice cold water, it’s like heaven.
Then keep refilling the frozen bottle from the others. After a few minutes in the (now semi frozen) bottle, the refilled water gets ice cold.
During the day the ice gradually melts, but as long as there is some ice left the refilled water will be cooled by it.
You can keep drinking and refilling this for a full days supply of ice cold water.
Your welcome.