Hi - 16 months is still pretty early for water. My pediatrician recommends my boys continue drinking mostly whole milk until they are 5 (their little brains need lots of natural fats to continue developing at the speed they need to), and to limit how much water and juice they drink, because too much water can cause diarrhea in infants, and juice dumps too much sugar into their little systems.
If it's just a little water here or there to keep your toddler hydrated, try soaking a fruit tea bag in cool water to add a little flavor, without using sweeteners or chemicals (orange, raspberry, peach and other fruit teas are usually all-natural and easy to find at any grocery store).
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