How best should a girl decline the offer of a drink?

Many guys offer a drink to the girl. The expectation is that she will return the favour by sleeping with him. How can a girl put an end to this line of thought? Should the girl

accept the drink and decline to sleep with him
tell him upfront that she will not sleep with him, drink or no
politely decline the offer, and offer him a drink
Select gender and age to cast your vote:
How best should a girl decline the offer of a drink?
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