Nearly half of the 3,000 parents polled said their children ate more junk food on a car journey than in any other situation - and a third said they felt guilty about it.
However, one in four said the plan often backfires with children getting hyped up due to too much sugar.
One in three parents have installed a DVD player in the car to keep the children entertained.
In fact, a same number of parents let their offspring dictate the choice of music, even it if is Bob The Builder or nursery rhymes.
But many more play games with the children such as I Spy or encourage reading.
"Parents should go prepared with more than treats. There are plenty of travel tips and games that can be downloaded free to avoid the 'are we there yet' moment," the Daily Express quoted Rob Law, spokesman for car seat makers www.boostapak.com, as saying.