Why is this targeted at chains with 15+ locations? Is the soda in a single location mom&pop restaurant any less bad for you? No. Why is this not just a blanket rule for the city?
Small local laws like this tend to gain a lot less traction when they pile up to be a larger (relative) load on smaller, local-only businesses. Rather than not have anything pass, people prefer to pass something which still has 80% of the benefit but only 20% the resistance. Only targeting large chains, at least initially, is a way to move that needle over getting nothing out of principle.
If successful/popular, then it's much easier to pass full coverage later.
How is this onerous? You update the website your QR code points to. It's not like you have to print up new menus. If you still have menus, just print up a sheet of stickers that you smash onto the menu. Malicious compliance can be used
If successful/popular, then it's much easier to pass full coverage later.