Are the sentences 这个杯子有一点儿水 and 一点儿水在杯子里 correct?
这个杯子有一点儿水 (this cup has some water) sounds like 这个杯子 is the subject and it possesses some water
A better phrasing should be 这个杯子里有一点儿水 (inside this cup, there's some water)

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一点儿水在杯子里 (some water inside the cup) lack a verb, thus make it an incomplete sentence
A better phrasing should be 有一点儿水在杯子里。(There is some water inside the cup)


这个杯子里有一点儿水 emphasizes the cup (pay attention to the cup, there's some water in it)

有一点儿水在杯子里 emphasizes the water (pay attention to the water, it is in a cup)


You can use either one