I still feel like we probably would have adopted adding sugar to tea to fight caloric deficiency somewhere in the last few thousand years if that made a measurable difference. Especially considering sugar cane is native to India and south east Asia, it was more abundant and accessible in Asia than western Europe.

I'm not saying sugar doesn't add calories, I just don't think it would be that big of an improvement.

A parallel I can think of is how Turkish cevze coffee is traditionally most often unsweetened, much like Italians drink espressos after breakfast, but the UK/US will have sweetened coffee as the norm. The beverage which serves a social and almost ritualistic function has been adapted and turned into another marketable treat in the Anglosphere.

Edit: either that or the working class in western Europe and UK/CAN/AUS had access to such shitty quality coffee and tea grit that they have to make it palatable with sugar, and then the claws of capitalism came along and turned it into a marketable treat