It comes as Devon and Cornwall Police's month-long campaign "Life Legend" returns to the region.
The force said drink and drug driving was among the most common causes of serious injury and death on the roads in the region.
Last winter, the force arrested 952 people for driving under the influence.
The scheme will run until Monday 1 January 2024 and drivers buying a soft drink in one of the participating venues will receive a voucher to get their second drink free of charge.
Sgt Owen Messenger of the road casualty reduction team said "even the slightest amount of alcohol or drugs" increased the risk of harm.
“If you think you are safe to drive after drinking or taking drugs, think again," he said.
“Despite long-term reductions, drink and drug driving still accounts for 15 per cent of road deaths and almost 10,000 casualties nationally each year.
“Tackling drink and drug driving is a priority for Devon & Cornwall Police. Our officers will be out in force, rigorously targeting those who are a danger on our roads, day or night."
Alison Hernandez, Police and Crime Commissioner for Devon, Cornwall and the Isles of Scilly said: "Drink driving is unacceptable – it puts the driver, passengers and innocent members of the public at substantial risk.
“Please, don’t risk it – take advantage of this offer and get free soft drinks for your designated driver. Let’s make sure everyone gets home safely this Christmas.”
A social media campaign will run alongside the scheme and people can find out about participating venues on the force's website.