We had a freestyle machine at my old office.
I have never had a problem with one. It uses boxes that almost look like printer cartridges, and sensors that detect levels. You will never have an issue of your drink running low on syrup and tasting like crap like can happen with soda fountains. What you want will just gray out.
I drink coke zero constantly, diet coke if that’s all they got, and never regular coke. The only place where that tastes markedly different is my local Arbys. Their fountain coke zero is super sweet, like there is too much syrup to water. If it was a one-off occurance I might suspect they accidentally plugged the regular coke in, but it’s like that all the time.