What a lot of parents would do is buy tofu but not pizza. They control all the money, so that's easy. They make tofu really convenient becasue there is always plenty around, and pizza really inconvenient because there is never any around. Requests for money to eat at a tofu restaurant are always granted. Requests for money to eat at a pizza restaurant always get replies about money not growing on trees. (BTW, apples grow on trees, and apples are worth money. So that saying is kinda silly.)
In the kid's life, tofu and pizza aren't fighting a fair competition for a place in his diet. Suppose the rational way to decide what to eat involves considering the price, convenience, nutrition, and flavor of foods. Of course there are other factors, but those are good enough. The parents make pizza less convenient and tofu more convenient. So they tip the scales. Whatever the rational evaluations of the foods are, they've distorted it. If tofu would normally win 40 to 25, now it wins 50 to 15. So the kid gets the wrong idea of the real value of the foods. The parent is spreading irrationality. The parents don't care about the truth as long as they get their way.
A good way to think of it is that the parent could do the same thing, except in favor of pizza and against tofu. It's totally arbitrary. Whenever the parent could reverse what he's favoring and disfavoring, then it's clear that the parent's policy doesn't depend at all on what the truth is. Maybe he's using reason, but maybe he's using whim. If it's whim, how's he going to find out? His policy doesn't have a mechanism to correct that error.
This is an example of how parents try to make their kid do what they consider best, instead of trying to find out what really is best. They can do it with anything that costs money.
Another resource parents control is transportation. They can hesitate more and smile less when asked for transportation to one place, and behave in the opposite way for another place. That is a way of distorting the value of the places to their children that bypasses reason and disregards truth.
Another resource parents control is what they will help with. Parents know parenting is a lot of work. Good parents are prepared to do it. They change diapers, cook meals, wash clothes, clean messes, patiently answer some questions, read books aloud, and so on. But what if their kid wants help, which is his right, doing something they don't approve of? Then conventional parents resist and try to impose their values on their kid. They deny him the help that is his right, and which they would give if he were doing something they approved of. And often they lie about it. When the child wants one thing they say it's too much work and they are tired, but then if he asks for help finding books about tofu recipes suddenly they aren't so tired anymore and are ready to be very helpful.
Manipulation of these sorts is designed to control the child and make him behave in the ways the parent considers best, both when the child agrees that's best, and also when he doesn't. TCS instead is concerned with figuring out what's best, especially when there is a disagreement, and finding an answer that doesn't distress anyone or cause suffering.