Spectators at the Olympic Games will not be allowed to take drinks or liquids in more than 100ml containers, like sunscreen, into 2012 venues.
Games organisers Locog have set out forbidden items in their ticket terms .
Sports fans and family groups have raised concerns about heat and expense at the 27 July-12 August Games.
But Locog said free water would be available across the venues, and the rules, including on how much food people can take, were being finalised.
Food is listed as a restricted item on Locog's website, but a spokesman said how big a picnic people would be able to carry in was "still under discussion". As was the size of sunscreen bottle that would be allowed.
He said security checks on people entering the Olympic Park site and other venues would be on a par with the "mag and bag" security seen at airports, where bags go through magnetic scanners and people are searched and where liquids in more than 100ml containers are banned.
Any liquids above that capacity would be removed, but people would be allowed to keep their bottles to fill up once through security, he added.
According to the current terms and conditions for Olympic ticket holders, items that cannot be taken into venues include:
- Food, except baby food;
- Alcohol and soft drinks, except baby milk and medical supplies;
- Liquid in containers over 100ml;
- Bottles or glass containers;
- Flasks and thermoses.
The ticket sales purchase terms also set out, in section 19.2, other restricted items including large umbrellas, drugs, horns, whistles and drums, fireworks, flagpoles, weapons, ammunition, firearms and explosives.
The terms cover Olympic Park, the venues within it, and the existing sporting venues Locog will commandeer for the period of the Games, across London and the rest of the UK.
Critics have said the rules covering food, drink and containers like those for sun cream could add unnecessary expense and inconvenience to a day out at the Games.
During the Games, Olympic football will be staged at Wembley Stadium; Cardiff's Millennium Stadium; City of Coventry Stadium; Hampden Park, Glasgow; St James' Park, Newcastle and Old Trafford, Manchester.
Football Supporters' Federation chair Malcolm Clarke said while restrictions during normal matches varied between stadiums, "airport" level security could spoil the Olympics for some.
"It sounds somewhat OTT. If you get a hot afternoon and you're there for several hours, people are going to want to take a bottle of water - in line with good medical advice."
He also raised concerns that people would be delayed by security searches.
"At football grounds it's a very inefficient process, it's a sort of 'pat down'. But anyone trying to take in an offensive weapon with half a brain could take it in.
"It's the worst of both worlds - sufficiently intrusive to be annoying but not so thorough to be productive. If they are starting to do 'airport security' it could detract from people's enjoyment."
Tara McBride, spokesperson for the Made for Mums parenting website said the restrictions could spell a "nightmare" for parents who planned to take along babies and children.
"The whole process of going to the Olympics should be a once in a lifetime event, not hours of preparation with a heavy heart," she said.
"For families travelling perhaps hundreds of miles to London, it's an extra level of logistical planning and headache and expense.
"Places that prevent you taking in your own stuff, usually sell you stuff as soon as you get in the door. It's going to create a lot of ill-feeling with families.
"Times are tough and people are already probably stretching their budgets just going. It's ridiculous. You're going to be there all day."
During the Games, archery will take place at Lord's cricket ground. Barmy Army spokeswoman Becky Fairlie-Clarke said she recognised people had to be safe at Olympic venues, but there must be enough staff to carry out security checks without holding back fans.
If ticket holders wish to buy food items within Olympic Park they will have to use cash, or a Visa card, one of the sponsors of the 2012 Games.
McDonald's will be the only branded food outlet in Olympic Park but there will be other non-branded caterers selling a wider range of food and drinks, including alcohol.
For some venues outside Olympic Park, where Locog will take control during the Games, the controls are tighter than their usual operating restrictions.
- At cricket ground and Olympic archery venue, Lord's, spectators are usually allowed to take in food and drinks including one bottle of wine or two pints of beer.
- At Olympic tennis venue Wimbledon, spectators are also allowed to take picnics, a bottle of wine or two 500ml beers, although glass is not permitted on the show courts.
The rules are also tighter than they have been at the test events held at temporary and permanent Olympic venues. There, small picnics and soft drinks in cans and plastic bottles have been allowed, with up to 500ml per person permitted.
Some 3.5 million tickets have been sold to 850,000 people, according to Locog.
The Locog spokesman said its rules for ticket holders were still being decided, ahead of the Games, and ahead of tickets being sent out.
He said of planned entry checks: "It's essentially the same as what you go through at airports, when your bag goes through the scanner and you get searched when you go through security.
"Liquids will be the same as at an airport, you won't be able to take liquids through. If you've got a bottle of water you might be asked to empty it but you'll be able to take that bottle in and fill it up when you get to the other side."
He said free water would be available, but how it was provided, such as in fountains or taps, had not been ironed out.
He said security, venue and police staff were still reviewing what could be carried in, including sunscreen and food.
"Where we are trying to get to is, if you come with a backpack with some sandwiches in, that won't be a problem," he said.
"It would be more of an issue if you came with a massive picnic hamper. With the numbers here, you have to get people in, in large numbers, as quickly as possible. You don't really want people coming in with massive bulky bags."
Sunscreen would be allowed, he said, but organisers were still looking at the size of bottles.
He added that Locog's food vision , for catering at the Games, should mean catering options were "better than your average sporting event".
The document pledges to provide free drinking water and deliver "a tastier, healthier, greener Games", for example by providing a "diverse range of food and beverage for all customers, catering for all dietary and cultural requirements, that are high quality, value for money and accessible".
It says food must be red tractor assured - meeting internationally-recognised food production standards - and UK-sourced where possible.