Pop (aka fountain drink) machines basically don’t exist.
First, I hail from the northern United States, so fountain drinks are known as “pop”.
There are two restaurants in the UK that I know of which have self-serve pop machines: Subway and Nandos. These two restaurants are havens for hangover days when I just want an “on-tap Coke”. Seemingly every other restaurant serves bottles or cans of pop. Beverage guns (found in American bars and restaurants) are also really, really rare. Want a gin and tonic? The tonic will be poured out of a single-serving bottle, not out of a beverage gun. Americans and their guns…
Below is a pop machine in the US. It’s like something out of the future. The first time I encountered this being, I wasn’t sure what to do and had to call in the help of my siblings. This machine can make approximately 1,600,000 flavors of pop.
Below is a pop machine at the Maidenhead Subway. This machine can make four flavours of pop because no one in the UK would ever fathom mixing flavours together. (Do you see what I did there with flavor v. flavour?)