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?