Hairdressers and beauty salons could be shorn of £20,000 if they offer complimentary wine or champagne to customers, police have warned.
Staffordshire Police said officers found "quite a few" businesses offering free drinks without the proper licence.
The force said such offers may be "well-intentioned" but are against the law if businesses do not have the clearance to sell alcohol.
Punishment for breaching the law is a fine of up to £20,000, up to six months in prison or both.
Inspector Paul Prenter, head of the force's licensing department, said: "We want to have a positive relationship with businesses in Staffordshire, which is why we want to provide this warning first.
"Providing alcohol to customers without a licence is a breach of section 136 of the Licensing Act and is a criminal offence.
"Please ensure your business is not giving alcohol to customers, otherwise our licensing officers will be in touch and it could result in a hefty fine for your business."
Martyn Brindley, Stoke-on-Trent City Council's strategic manager for public protection, said: "It is very important that all businesses are aware of the laws regarding serving alcohol on their premises and that they abide by them."