When to use ‘usted’ in more formal sentences

This might be a bit of a beginner question, but I'm a bit confused. So, if you were talking to someone in a casual context and asking if they wanted a glass of water (just a random example), you would say:

¿Quieres un vaso de agua?

And for more formal sentences, you can say :

Quiere un vaso de agua?

And the 'usted' is implied by the conjugation. But, if you want to add the usted for more formality, would you say

¿Usted quiere un vaso de agua?

or

¿Quiere usted un vaso de agua?

Or does it not matter? I'm just a bit confused on where the 'usted' is supposed to go. Thanks in advance.

submitted by /u/Embarrassed-Phase349
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