There is so much sugar in a can of regular soda, it makes it sink. My kids can be crazy sugar junkies so helping them understand how much sugar is in their food is a step towards them learning how to manage their own nutrition.
What you need:
Can of regular soda
Can of diet soda
What you do:
Fill a sink with water.
Put a can of regular soda and a can of diet soda into the sink.
Notice which can sinks and which can floats.
Why did the regular soda sink? Regular soda often has over 40 grams, or nearly 10 teaspoons of sugar! That much sugar makes the can sink. Diet soda has chemical ingredients that weigh much less than sugar, so it floats.