On hot bike rides if I stop somewhere, I have had a cup of coffee.. Either that or a natural fruit juice as an energy booster. I've never drank Gatorade or other energy drinks even during years where I was cycling triple the total annual mileage compared to now.

I don't see any relationship between coffee and weight gain for myself. For the times I did get unwanted weight, it was too much of other types of food creepin' into the diet. In fact, occasionally to stop myself from having any dessert, I'll opt for a nice hot frothy cafe au lait (steamed milk with abit of coffee). No sugar.
(But I'm not much of a purist. I do have a dessert.)

But the way how I drink coffee is just with a bit of milk. (Cream only if milk not available.) No sugar. And it has been since my early 20's. At home, it's tea. More of a costs-saving issue.