Do we drink enough?

Usually I live on coke (not the diet stuff , migraine before I finish a glass of that vile stuff ). A hot chocolate if I’m very cold. Very occasionally orange or apple juice, only during hot weather. one can or pint of lager in the evening with tea. So swapping out some of my coke with water is a massive change & challenge for me. Still not drinking a huge amount. As I’ve never managed to drink the supposed 2.5lt of liquid a day. Does anyone? I’m still having my glass of coke in a morning (when normal people would have tea or coffee). I tried cutting that out a while ago and just spent the rest of the day with a headache. So not cutting out my morning hit of sugar.