kitchen

Lock them in a room with ingredients they have to cook in order to eat or with ingredients that taste awful without being cooked and leave them with a few recipes. In a week when they finally escape and call the police on you they'll be cooking for sure.

Offer to make something the really, really like, but only if the help. Bribe them with cookies. Or cookie dough.

Depends on age. Yoinger than 8, give toys or ur phone if they do good
Older than 8, bribe with money

It’s impossible

Teach them the way of the spacula