You can, but it won't make the beer taste like fruit, honey, or coconut. Once the sugars have fermented out, the remaining taste is not always what you would expect. The added sugars will affect your ABV, but so will the added water. Depending on the recipe, it could raise or lower your alcohol content.
Yeah, for the most part honey will disappear completely. Coconut I have heard you need to roast it before you use it, and different fruits have to be used at different stages in the process to get the right flavor from them. Research the exact fruit you want to use to get an idead the different methods and make a choice on what kind and how much flavor you want to impart.