I read that the syrup is stored in these special tanks, and when it's mixed with the carbonated water, it comes out as the best tasting, freshest Coca-Cola you can get. It's always tasted amazing at McDonald's. Almost like bottled Coke.
Supposedly McDonald’s is the only business that gets the syrup distributed in metal kegs. Everyone else gets the plastic bags, which could lead to some taste difference.
I am pretty sure I could blind taste test canned vs bottled soda.
AFAIK they are completely phased out in the soda industry (including McDs). They are very popular in the home beer brewing community because they are easy to clean and the right size for your typical homebrew batch (20 litres). They've become difficult to obtain in recent years because they are not being used in industry any more so there's no secondary market.
Some players are making them new, but they are quite expensive. I used to have a couple of regular beer kegs on "long term loan" from Heineken because I was not able to source cornys for cheap.
Definitely depends on the store in my experience (Aus), I think some may not maintain their machines as frequently/well, or maybe even deliberately watered down. Glass bottle Coke is the best coke imo.
