A couple of reasons to limit caffine consumption in your little ones. First: caffeine is a diuretic that causes the body to eliminate water (through urinating), which may contribute to dehydration. Caffeinated beverages contain empty calories (calories that don't provide any nutrients), for young developing bodies, maintaining nutrition is essential to proper growth. Caffeine is a stimulant, most children wouldn't like the taste of black coffee, so sugar and milk are likely to be added, sugar is also a stimulant. With all the ADD / ADHD rampant in our society, it isn't hard to imagine the increased consumption of these kinds of stimulants (especially through soda beverages) don't contribute in someway. If you're going to promote caffeine consumption in your little ones, stick with something like chocolate or cocoa, which at least has known health benefits.