The one that turns up everywhere in the house — on the counter, in the car, by the bed — because it keeps water cold long enough that you actually remember to drink it.
View on Amazon →Big enough that you don't have to refill it three times a day.
Drink one-handed, no unscrewing a cap with every sip.
Keeps drinks cold for hours, even left in the car in summer.
For anyone who needs a constant visual reminder to drink water — and likes that reminder to look good on the desk.