Some flavors that work great include strawberry, peach, lemon, pink lemonade (add sliced lemons) and passion fruits.
Keep in mind that this drink has zero calories, so it is great if you're dieting, don't want to add liquid calories or are diabetic.
However, if diabetic, do watch what artificial flavoring is in your liquid water enhancer as some have sugar alcohols that set off blood sugar spikes and cravings.
You could also sub powdered flavoring, such as Crystal Light, if that is what you have on hand, but it is more potent, so add sparingly and taste frequently.