Some say all it takes is a normal type of vinegar that you can buy in a grocery store.

At least this is safe, as it is used in cooking or cleaning.

All I'm sure about is that an adequate solution of vinegar can burn the leaves of a weed and leave them withered. Some weeds resist this more than others, but I have experienced that it takes more effort to actually kill weeds down to the roots.

Before

After two weeks of thorough spraying.

These sheep sorrel did not regrow from their roots.

I bought 50% vinegar concentrate.

I diluted it equally with water yielding a 25% strength.

I spray on weeds making sure to completely douse each and saturage the soil down to the roots.