marlingardener, your post made me curious, so I looked and found a website that said most household vinegars have an acid content of 5%. Balsamic and White wine come in highest at around 6-7%. That's some expensive weed killer!
Upon re-reading my post, and looking at "pickling vinegar," I'm wondering if I may have found a use for all the pickle juice left at the bottom of a jar. Seems a waste to dump it down the sink, and
I don't want to put it in my compost. Weed-killer...hmm.
unsure300, I've always gone straight to vinegar because I like "pretty much foolproof," but I also remember Mom telling me that pouring boiling water on a plant will often kill it to the roots. You might have to "water it," by which I mean pour slowly, directly on the plant, allowing the heat to get down to the roots. I don't know how tough your grass is, but "free and experimental" might be worth a shot. (And then come back and tell us if it worked!!)
Oh and,
Welcome to the forum!!