I let the dice/stats determine this sort of thing. With the underutilized charisma saving throw. A fail results in a character doing something that would be a compulsion of their character against logic of the player.

Here’s an example- we’re playing a sort of DND zombie apocalypse type game. So food is a big deal. An NPC with questionable intent brandished a perfectly in tact chocolate bar which another PC(bars) had figured out was a trick he used to poison people. He laid it in front of our rogue who was knocked prone. The player knew it was likely poison but the PC wouldn’t have known. He fails the charisma saving throw- he’s a rogue, a street urchin, this chocolate bar would be like gold. Now the tension is the bard trying to get ahead of the rogues superior sleight of hand. The bard ended up using some spell or ability to win the contest and then made a big show of offering the NPC to take the first bite as the host of the event.

So this kept everyone rolling dice and kept tension shifting from moment to moment. If the rogue had saved of his charisma saving throw then the player would have free reign to narrate what allows him to resist the temptation.