Alcohol (vodka) concentration+testing

Friend's brother has a small bar- he bought quantity of vodka (well known brand) at wholesaler. customers said something wrong with taste of vodka. Obviously, he is not happy- and wants to independently verify what is in bottles... Any advice where to arrange?

hey should try to get in touch with the importer of the brand. They will quickly tell him if its the real stuff or not.

Vodka should have very little or no taste, colour or odour. Has he tried it neat? Is there a flavour?

Is he serving it with ice, and if so, what is the quality of water used for ice making like? If there is any taste to the water, that's the likely source of the issue.