Certainly a belief among some that soda from a glass bottle tastes notably better.
I prefer glass bottles for my beers.
Ahhh the subtle flavours of rat shit. I've never seen someone wash the top of a can before opening it. I mean, would you go around licking random surfaces that other hands have touched, rodents have scurried over and defecated on, etc?
This is at least partially a myth.
Here's a study which found no sucrose in Mexican coke: https://onlinelibrary.wiley.com/doi/full/10.1038/oby.2010.25...
Though, it is complicated because there are multiple bottlers making multiple different coke products, and even the same bottlers could shift what sweeteners they use over time, presumably based on pricing.