Most parents feel guilty about the contents of their child's lunchboxes, according to a poll.
It suggests that concern over whether a youngster will eat what has been packed for them is the most common factor in what mothers and fathers choose to include - ahead of whether or not the lunch is nutritious.
Action for Children, which published the survey, said getting children into good eating habits does not have to be daunting and "can make a lifetime of difference".
The small-scale poll found that the most popular items for a school lunch box are a ham sandwich, a yoghurt, a packet of crops and an apple.
The most popular drink was a carton of juice.
The findings come as children anticipate returning to school next week after the summer holidays.
Overall, 75% of British parents of children aged five to 13, who pack a school lunchbox, said that they have felt guilty that their child's lunchbox is not healthy enough.
Asked to rate the most important factors when choosing what to put in a packed lunch, the most common response was "feeling confident that my child will eat what I've packed", followed by "that my child has a nutritious lunch".
Emma Horne, Action for Children England South director, said: "Most parents understand the pressure to pack a lunchbox that will come home empty at the end of the day. And it makes things even harder when you're time-poor and budget-conscious.
"But it's clear that childhood obesity is a problem we need to tackle, to save our children from suffering physical and mental health problems when they grow up.
"Getting eating habits right in these early years isn't as daunting as it seems with the help of a few clear tips, and it can make a lifetime of difference."
The poll comes amid continuing concerns about obesity levels among children.
Around a third of children are overweight or obese by the time they leave primary school, according to official figures.
And according to data from the latest National Diet and Nutrition Survey, published in June, while four-to-10-year-olds should not have more than the equivalent of five-to-six sugar cubes per day, they are consuming 13 on average.
The YouGov poll questioned 535 British parents with children aged five to 13, including 385 who pack a school lunchbox, between August 8 and 10.