Katy, my DS has had a couple of very small sips from a coke on maybe 2 occasions when we've been eating out. I wouldn't encourage fizzy drinks but it's been so rare, like when I let him have real cake or dessert (ie not sugar free, not home made). Funny boy though, he will more often than not refuse anything with sugar in and 'demand' fruit instead.
I think it is the level of minerals in the mineral water as well as the sodium that isn't good for them (like when a kettle is double boiled, it mineralises the water or something)
I think the supermarket cafe is just not set up for giving tap water. If the water comes from a tank it's ok to boil it in the urns they have for tea and coffee or to cook with but wouldn't be classed as drinking water.
My brother had no choice but to make all his LOs formula bottles from mineral or spring water from NB because he lives in China and doesn't have clean tap water (as a widower there was no option for breast feeding). In that case bottled water is the safer option but in the UK we are advised to stay away from bottled water unless in emergency circumstances. I was a bit worried about my brothers LO having mineral or spring water but see there was no other option for him.
