The RAC has launched a soft drink called RAC 124 - named after the amount of caffeine in milligrammes contained in the drink - to help raise awareness of the danger of falling asleep at the wheel.
But one of its major rivals, Green Flag, warned fleets against reliance on high-caffeine drinks to prevent drivers nodding off.
A spokesman for Green Flag said: 'Although drinking strong coffee or energy drinks may help to alleviate fatigue in the short term, we advise drivers that the only real solution to tiredness is sleep. Taking proper breaks during long journeys is also essential, as monotonous stretches of road can lead to drowsiness.'
Company car drivers keeping to unrealistic appointment schedules are likely victims of tiredness while driving, and research has shown that up to one in five road accidents is caused by tiredness.
Mary Williams, chief executive of road safety organisation Brake, added: 'Driver tiredness is a serious and hidden killer. Caffeine drinks are only part of a series of measures drivers should take to avoid drowsiness.'
The RAC said the drink was not meant as an alternative to taking regular breaks and naps. And drivers should only continue with their journeys if they felt fit to do so.