What is the ruling on selling live chickens according to their weight and vinegar that contains 6% alcohol?
It is permissible to buy chickens according to their weight. This is the basic rule. Moreover, we do not know any proof that contradicts this rule.
It was authentically reported that the Messenger of Allah (peace be upon him) said:
"If a large amount of anything causes intoxication, a small amount of it is prohibited."
If a large amount of vinegar causes intoxication, a small amount of it is forbidden. It will be regarded as wine in this case. But if a large amount of vinegar does not cause intoxication because the ratio of alcohol is too small and has no effect, then it will be permissible for you to sell, buy and drink it.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.