On the topic of fizzy drinks, these aren't necessarily off limits for diabetics. Fizzy drinks containing sugar should be avoided, as should fruit juices, but fizzy drinks with artificial sweeteners generally have little/no impact on blood glucose levels. Many "no added sugar" squashes/cordials are also suitable for diabetics, as several threads on the forum have discussed. Ultimately, it entirely comes down to which particular artificial sweeteners are used in products, and while some can cause a glycemic response, many commonly used in diet, zero sugar, and no added sugar soft drinks or cordials don't cause any issues for most people with blood glucose levels.
While there are potential health impacts of artificial sweeteners, it's down to people to assess whether that's a concern of theirs, but from a blood glucose management perspective there are many other drinks options than just water.