Often in interviews I came across problems in the genre of "quantify". Such tasks are quite common when evaluating beginners in intellectual professions. In them, you need to come up with a formula for assessing this or that indicator on the fly and, using common sense, calculate its amount. For example, how many trees grow on the ground, or how many table tennis balls can fit on an airplane. It is expected that the candidate should estimate the volume of the ball, clarify how many-seat aircraft are meant, estimate its volume and, dividing one by the other (preferably in the mind), get the result.
Another genre of brain teasers is business. Its essence is that according to the condition in the company X, profit falls, and you need to understand why this is happening and give recommendations. It is expected that the candidate does not know the specifics of the industry, but thanks to his broad outlook and sharp mind, he quickly delves into the essence of the problem and proposes a solution.
I recently discovered another genre - event organization. For example, a candidate needs to organize a hackathon in, say, Seattle. What will be his actions?
But if you think about it, there can be many such species.
Organize production (for example, clothing, electronics, food, etc.)
Build an investment portfolio
Suggest a web application architecture
Make a travel plan
Save humanity from coronavirus
And much more
All these tasks are united by the fact that initially there is no correct answer to them, but they allow you to assess the speed and adequacy of the candidate's thinking, his horizons, imagination, and, of course, the ability to ask the right questions. Please write in the comments what other interesting non-technical brainteasers you can use to evaluate a candidate.