My boyfriend has a rat in his apartment complex. What foods could we leave out for it that are poisonous?

There's a hole under his sink where the rat has come in before (he's seen it, too), so we want to draw it out onto a sticky trap. But I was wondering what foods are very bad or poisonous to rats? We want to draw it out, so it'd have to be a food the rat would want to eat...but at the same time, just in... show more There's a hole under his sink where the rat has come in before (he's seen it, too), so we want to draw it out onto a sticky trap. But I was wondering what foods are very bad or poisonous to rats? We want to draw it out, so it'd have to be a food the rat would want to eat...but at the same time, just in case the sticky trap doesn't work I wanted to know if there was a really bad food for them to finish the job.

We don't just want to use straight up poison. If that rat is going to die, we'd like it to enjoy its last meal, then give it a very quick death.

I've heard that peanut butter is a big no-no with pet rats because they can choke on it. Do pest rats have the same problem? And what else could we put on the sticky pad for it to be drawn to?
Update: We can't keep this thing alive, nor board up the hole. There are naturally holes under the sink cabinet/drawers, and my boyfriend would probably pay a hefty fine for trying to board those up. Not to mention, that would leave the rat able to get into his drawers still, and live in his walls (chewing on wires,... show more We can't keep this thing alive, nor board up the hole. There are naturally holes under the sink cabinet/drawers, and my boyfriend would probably pay a hefty fine for trying to board those up. Not to mention, that would leave the rat able to get into his drawers still, and live in his walls (chewing on wires, perhaps?).

We really don't want to go out and buy poison. It's too cruel to us. And there's no way to trap this guy besides the sticky trap. But if we do catch it, he lives in a city. If we let it go, it'll just end up in another building very quickly (where they might use far crueler methods of killing it). We want to put the poor thing to death as quickly and painlessly as possible (we both love rats...just...not crawling around destroying his apartment).
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