There are substitute goods, but the fact remains that they simply don't have the distribution and marketing that soda has. You can eat a bag of marshmallows but there are no marshmallow vending machines, that I am aware of.
Ease of access is largely irrelevant when people need to eat either way so they can just make larger portions, eat a few extra chips when snacking etc.
Don’t get me wrong obesity does relate to the overall abundance of calories, my point is that singling out soda or candy isn’t going to do much by itself.
There are direct observations of the link between workplace soda availability and waist circumference. You can wave these away as "not long term" I guess, but it's the best evidence available.
The fact they didn’t mention a weight reduction or BMI changes suggests they didn’t observe any changes in weight / BMI.
I’ve looked into this a while ago and while consumption falls no studies showed a change in weight from soda bans. Unless you have something more recent?
Critically the biology around weight loss is complex but even with very intentional diet changes people rarely keep weight off long term.