Yeah, I read somewhere on another forum (a triathlete one I think) that @Dr_Alex_Harrison often carries two 1 litre Zefal Magnum bottles on training rides, the front one containing the concentrated sugar mix and the other one just water to wash it down. He treats the sugar mix as a glorified energy gel (i.e., you always wash a gel down with a swig of water). Don’t know if he does this to aid absorption and digestion, or from a dental hygiene point of view, or both.
Both. Mostly the first.
And ease of swallowing/breathing afterwards.
I stand corrected. My osmolarity math was correct, but my sweetness math was wrong. Sucrose is very slightly more sweet than malto:fruc. Probably not enough to matter.