cherrybim- neither you nor feif un addresses coffee, which i clearly remember is OK for kiddush (daytime) and havdalah. the logic is inescapable- you always serve coffee to guests. I don’t understand R’Moshe zz’l logic about tea. All drinks are ‘water” including wine (especially if it is “mozug”). please indicate the place of the actual teshuvo.
concerning Pepsi ,and I imagine the same goes for coca cola, I understand rav Ruderman ‘s psak although in my yeshiva they said that soda is drunk to quench thirst , not to honor guests.