It found that energy drinks contained up to 78g of sugar per 500ml - more than three times the 25g limit for women proposed by the Scientific Advisory Committee on Nutrition.
AoS has called for sales of energy drinks to be banned to children under 16, and said children and adolescents should be aware of the 'excessive and worryingly high' levels of added sugar.
Out of 197 energy drinks surveyed by AoS, 78 per cent of these would receive a 'red' label for sugar content, while 101 contained the same amount or more sugar than Coca-Cola, which contains the equivalent of nine teaspoons of sugar per 330ml can.
Per portion, the worst offender was Rockstar Punched Energy plus Guava, which contained 20 teaspoons of sugar per 500ml can.
Per 100ml, examples of high sugar energy drinks included Sainsbury's Orange Energy Drink (1L) with 15.9g, Rockstar Juiced Energy with mango, orange and passion fruit (15.2g), Red Devil Energy Drink (15g) and Lucozade Energy Pink Lemonade/Caribbean Crush (14g).
The charity said there were similar products on the market with considerably less sugar, for example Monster Khaos Energy and Juice, which contained 7.8g per 100ml, or about 50 per cent less than the highest sugar-containing energy drinks.
Last year the National Institute for Health and Care Excellence (Nice) issued new draft guidance saying that even people of a normal weight should be urged to avoid sugar sweetened drinks including fizzy drinks, sports drinks, squashes and any other hot or cold drinks that contain added sugar.
AoS nutritionist Kawther Hashem said: "The level of sugars in a typical can is disgraceful. Free sugars increase the risk of obesity, type 2 diabetes and dental decay and we need to protect children and teenagers from drinking these products.
"Sugar-free options are available from some manufacturers but be aware these still contain high levels of caffeine or other stimulants, so are not a healthy option."
Graham MacGregor, Professor of Cardiovascular Medicine at Queen Mary University of London and chairman of AoS, said: "Children are being deceived into drinking large cans of this stuff, thinking they are going to improve their performance at school, during sports or even on a night out.
"In reality all they are doing is increasing their risk of developing obesity or type 2 diabetes which will have lifelong implications on their health. Type 2 diabetes is a leading cause of blindness, limb amputation and kidney dialysis - hardly the image of a healthy, active person."
British Soft Drinks Association (BSDA) director general Gavin Partington said: "These products are called energy drinks for a reason - they deliver a caffeine or glucose-based energy boost.
"They are now available in a variety of types, flavours and sizes, including a range of low and no calorie options, so that consumers have a much wider choice.
"BSDA members do not promote energy drinks to children under 16 and all products are clearly labelled in compliance with EU regulations."