It seems like for reduced calorie Coke specifically, it is marketed as "Diet Coke" or "Diet Coca Cola", in at least Australia[1], New Zealand[2], The United Kin

It seems like for reduced calorie Coke specifically, it is marketed as "Diet Coke" or "Diet Coca Cola", in at least Australia[1], New Zealand[2], The United Kingdom[3], India, Israel and The US[4]. [1] https://www.coca-cola.com.au/ourdrinks https://www.coca-cola.com.au/ourdrinks [2] http://coke.co.nz/ http://coke.co.nz/ [3] http://www.coca-cola.co.uk/brands/diet-coke.html http://www.coca-cola.co.uk/brands/diet-coke.html [4] http://en.wikipedia.org/wiki/Diet_coke http://en.wikipedia.org/wiki/Diet_coke