Flavoured water

No it is not true. Just because something is added, doesn't mean it magically is no longer water.

There's some question as to if coffee might be somewhat dehydrating, but I seriously doubt a cucumber is going to affect anything.

Mayo Clinic Excerpt: Although the "8 by 8" rule isn't supported by hard evidence, it remains popular because it's easy to remember. Just keep in mind that the rule should be reframed as: "Drink eight 8-ounce glasses of fluid a day," because all fluids count toward the daily total.

Snopes Excerpt: Regular coffee and tea drinkers become accustomed to caffeine and lose little, if any, fluid. In a study published in the October issue of the Journal of the American College of Nutrition, researchers at the Center for Human Nutrition in Omaha measured how different combinations of water, coffee and caffeinated sodas affected the hydration status of 18 healthy adults who drink caffeinated beverages routinely.

"We found no significant differences at all," says nutritionist Ann Grandjean, the study's lead author. "The purpose of the study was to find out if caffeine is dehydrating in healthy people who are drinking normal amounts of it. It is not."

The same goes for tea, juice, milk and caffeinated sodas: One glass provides about the same amount of hydrating fluid as a glass of water. The only common drinks that produce a net loss of fluids are those containing alcohol — and usually it takes more than one of those to cause noticeable dehydration, doctors say.

No, its not true.