Anakin stops and thinks - had the other offer not been there, had it been 'do you need more of a breather or are you ready?' he would have said yes, even if he wasn't. But 'do you need something to drink?'. "I want something to drink." He doesn't know if he needs it - he's always been thirsty since they were sold on Tatooine, and he doesn't remember much before, and while it's better now, he's still always thirsty.

Takes more than a couple days to make up for dehydration on scale he's endured, who knew?