Why does sugar dissolve in lemonade but not in cold coffee?

Question

Coffee shops have bottles of sugar water/simple syrup to sweeten iced coffee drinks. If you add sugar, it ends up in a grainy pile at the bottom. How come, then, sugar dissolves in drinks like lemonade? I'm not necessarily talking the mix, even when you just mix lemon and sugar in water?

Answer 1

The acidity helps eat away at the sugar.

Answer 2

Coffee is an emulsion of the many oils in the roasted coffee with the water, while lemonade is a slightly acidic solution. The result is that the solubility of the water in the coffee is greatly reduced and it is not able to dissolve any more additives, but the lemonade can because it has not been saturated yet.