Water in a Starbucks cup.
The Starbucks Etiquette Rule When It Comes To Ordering Water

As with any order at Starbucks, you should do your best to abide by certain rules when you order a cup of water, which is available free of charge.

If you want to order a cup of water at Starbucks, do so when placing the rest of your order so the barista can factor it into their drink-making routine.

Asking for water after the barista has made your other drinks requires them to go back to grab a cup, pour water, add ice, and take it back to you, costing more time.

Likewise, when you request a cup of water, you should always specify the size of the cup. The barista doesn't want you to complain about the default water option — a grande with ice.

If you would like a free cup of water with your mobile order, ask at the counter before picking up your order. Try to avoid asking for water at the pick-up point as you would in-store.