“If this was your money, would you invest it this way”.
This question worked well for many years as a corporate executive, asking the question of those who reported to me about the projects for which they were seeking support.
Usually, indeed, almost always, the answer was “Yes”. Clearly my last question had been accommodated before they got to the point of asking, and they knew it was coming, so made sure they could answer Yes before asking.
The added effect of this question was to ensure that there was a personal commitment from the managers involved, they had to look me in the eye and convince me that they had invested their credibility in the project.
This did not guarantee the proposal worked, that was not the deal, just that it was worth doing, and if it went pear shaped, there was accountability, and the opportunity to learn from the miscalculations would not be lost.
As a consultant for 20 years, I still ask myself the same question when recommending actions to my clients, “would I spend my money on this”
It still works.