why the hell did my sim drink his wife?! she was a total bitch and the funny part is, when she died, everyone cheered. i think she died via cowplant. the minute she died, he drank her. why do sims do that?

Well, maybe the fact that it makes them live longer helps.
I mean, think about it. Say you have a real cowplant growing in your garden. And a burglar tries to break in, and is eaten by said cowplant. If you found out that drinking cowplant milk would make you live longer, wouldn't you be tempted to put that burglar's misfortune to your own benefit?

She definitely died by being eaten by the cow plant. As Kimiko-Chan said, drinking cowplant 'milk' works like the elixer of life in that it adds a few days onto their life making them a bit younger. Sims can actually get a want to drink another sim, usually it will be an enemy. I find it hilarious that your sims all cheered when she died!

I love the cowplant as it's great for killing off ugly or annoying townies, but I tend to keep it in a locked room the rest of the time as I've lost sims to it I actually like when I wasn't watching.

Two of my sims that were sisters, after a big fight, wanted to drink each other. I actually find that sort of gross, drinking other people? Haha but funny story!