They are both correct and natural, but have different meanings. Howrver I suspect that you mean sentence 1. The 'so' linking the two parts of the sentence shows that the first part of the sentence is the reason for the second part, a bit like 'because' in reverse, the sentence would have the same meaning if you swapped the two halves and changed 'so' to because. Sentence 2, using 'and' does not imply that the first half is the reason for the second half

Hi Mari Kim Great question. Number 1 sounds more natural and is more grammatically correct. Why? You have stated that you "need 8 hours sleep" and then given a reason to what works for you. There are a couple of things that you can add. Instead of "so" you could replace it with "therefore" as this states that an explanation will follow. If you wanted to emphasise WHY you only drink those drinks, end your sentence with "therefore I only drink decaffeinated coffee and tea, as they do not contain ingredients that keep me awake." Number 2 is almost sounding like a list of things that you do - i e " I go to work every morning, and I only eat chips." - they are almost like 2 different sentences. Does that make sense?

First answer

i think first one is better than second one. cause the reason that you drink decaffeinated drinks is you need eight hours of sleep