Whether you use a jar of prepared marinara or make your sauce from scratch with canned plum tomatoes, there is always going to be a little bit of jammy, red residue in the bottom an on the sides of the container, whether that container be plastic, glass, or aluminum.
It’s never such a great amount of residue that one should feel terribly bad about tossing it out, but chances are you probably want to recycle the container, and you can’t throw a dirty, tomato paste-plastered jar or can in the recycling bin. (You want ants and rats and other vermin? Because that’s how you get ants and rats and other vermin.)
So, if you’re going to be rinsing the tomato stuff out of the jar or can anyway, you might as well toss it in your sauce, and you might as well rinse with wine. Even a cheap, slightly oxidized red will add more body and depth than plain, boring water. You can use your tomato-infused wine to deglaze a pan of onions or sausage, or add it directly to a simmering pot and let it reduce with the rest of the sauce. Either way, you will feel like a the model of culinary efficiency.
If you are working with a jar, just pour the wine in the jar, close it, and shake it; if you are working with a can, pour the wine in the can and give it a few swirls (and maybe scrape the sides of the can with a spoon or spatula). Then, dump the wine in the sauce or pan. Then rejoice, for spaghetti is coming. (And yes, you probably should give the tomato vessel one more rinse before tossing it in the the recycling bin—it’s the polite thing to do.)