The top five bad habits also include changing a CD and adjusting a sat-nav while at the wheel on the UK's busiest major roads, prompting a call by the RAC to remind drivers to take care at all times and ensure their focus is always on the road ahead.
The survey of 1,600 drivers found 57 per cent admitted to opening a bottle and having a drink while driving, 48 per cent said they change CDs, 35 per cent have eaten a sandwich, and 29 per cent are distracted by adjusting their sat-nav system. A further 15 per cent even admitted reaching for items in the glove box or footwell at the same time as driving at about 70mph.
These actions breach the Highway Code, which states: "Avoid distractions when driving or riding such as trying to read maps, inserting CD or tuning a radio, arguing with your passengers or other road users, eating and drinking."
Of the drivers who took part in the survey, the worst offenders were the 17-35 age group, where 61 per cent say they change a CD in the car and 41 per cent take their eyes off the road to adjust sat-nav systems.
According to the latest available statistics from the Department for Transport, distraction or impairment accounted for almost 14,000 accidents on British roads in 2012.
RAC technical director David Bizley said: "Motorways are the safest of our roads based on the number of accidents in relation to the amount of traffic they carry and the distance travelled, but more people are killed travelling on motorways than any other road type."