Best way to get rid of vinegar smell in poly barrel

[das fisch]

I acquired two food grade poly barrels that one held cider vinegar and the other balsamic. I have rinsed twice with water but have not gone further.
What's the best way to rid them of the smell? Want to use one as sap storage and the other as a head tank

[MISugarDaddy]

You might try washing them out with soap and hot water, then rinse them out thoroughly. I had to do that to a 275 gallon tank that I got to get rid of the vegetable oil smell that was in it. I scrubbed it well with the soap and then while I was rinsing it out I also scrubbed it too. Good luck with it.

[Scribner's Mountain Maple]

No expert, but I would try baking soda and hot water, a lot of baking soda and let it soak over night. May help. I hate to use soap on anything sap or syrup touches. White vinegar and baking soda do a nice job.