"What would you like to drink?"
Better English here would be a more formal "Which beverage would you like?" More informally you would hear someone say "你想喝点儿什么呢？" --- What would you like to drink?
Then again, given the imprecision in Chinese - English / English - Chinese translation sometimes, who cares?
The concept of “accurate” is not very helpful: nuances of meaning depend so much on context. In British English “What drink would you like?” might imply you were selecting from a limited list. “What would you like to drink?” is more open-ended about what might be possible.
Consider these two statements in English, maybe said to a waitperson at a restaurant: a) "I'll have the chicken" b) "I think I'll have the chicken".
On any given occasion you might say one or the other. If you actually think about it (like we are now), in hindsight you can explain the subtle difference and why you chose one over the other (something to do with your degree of certainty at the moment, or maybe you're just chronically on assertive).
But at the moment in which you (hypothetically) said one or the other of those things, odds are you weren't giving it any thought-- that's just what came out.
I think the difference between "xiang yào" and just "yào" in this exercise is essentially comparable to the difference between "I'll have" and "I think I'll have" (or "I want" vs. "I think I want") -- it exists, but is subtle, subjective, and highly situational, and no rule can tell you when to use which. Just experience.
The question immediately before gave me "你想要什么饮料" and provided the words "What would you like to drink" as the correct response ... and the very next question asked me to translate "What would you like to drink" into Chinese and did not accept "你想要什么饮料". That's frustrating.