I think Coke No Sugar is supposed to be the replacement for Coke Zero. They also aren’t identical as Zero/No Sugar uses stevia as the sweetener while Diet Coke

I think Coke No Sugar is supposed to be the replacement for Coke Zero. They also aren’t identical as Zero/No Sugar uses stevia as the sweetener while Diet Coke uses Aspartame. I will bit the rebranding of Zero to No Sugar might have also been an attempt to get ahead of legislation to tax sugary drinks.