Of course they know what sweet tastes like. I just took the difficult-but-responsible act of teaching my children to enjoy things that are not sweet, rather than the easy-but-harmful act of teaching them to crave sweets and other harmful substances. My eight year old also does calculus and completely understands the difference between kinetic and potential energy, and does mgh=1/2mv^2 to figure out how fast something is falling, or how fast she needs her bicycle to go before hitting the curb, such that it will have enough speed afterwards to keep upright. She'll also tell you all about gravity, thrust, lift, and drag and then tell you why the F-4 has so much anhedral on the horizontal stabilizer.
I guess it helps that my kids are outside playing, exerting energy and learning how things work, while many other children are snacking away in front of the TV all evening. Some parents go for easy. Some parents invest in their children.
Oops, I fed a troll. If it's an excuse to brag about my smart, healthy kids, then it was worth it.