Three popular energy drinks contain more caffeine per serving than the recommended daily dose for children, while two also hold more than the recommended daily intake of sugar for adults.
Three of the drinks tested - Coca-Cola's Relentless Energy, Monster Energy and Monster Khaos Energy and Juice - were found to contain 137mg, 143mg and 146mg of caffeine per serving, respectively, according to the watchdog's report.
Canada, one of the few countries to issue guidelines, says it is unsafe for children under 12 to consume more than 85mg of caffeine a day. No recommended intake is given for adults, because the amount varies according to body size and other factors.
A cup of coffee contains 110mg of caffeine or more, according to a previous Consumer Council report.
"Overconsumption of caffeine is detrimental to children and vulnerable groups such as pregnant women, and has been linked to health issues such as seizures, kidney failure and sometimes fatal conditions," council vice-chairman Philip Leung Kwong-hon said yesterday.
Leung said that while Hong Kong law did not require caffeine content to be specified on ingredient labels, the council would recommend that manufacturers print clearer labels and that stores stock such products in specific sections.
The World Health Organisation sets the recommended daily intake of sugar for an adult of normal weight at around 50g, although some WHO experts say the level should be closer to 25g.
Coca-Cola's Relentless Energy drink contains 50.5g of sugar per serving, while the Monster Energy drink contains 52.5g, the council found.
That's the equivalent of 10 to 11 cubes of sugar each, and equal to an adult's recommended daily sugar intake.
A spokesman for Coca-Cola Britain said the company did not market the Relentless Energy drink to children under 16.
"The pack is clearly labelled as having high caffeine content and isn't recommended for children.
"The sugar content is clearly stated as well," said the spokesman.
The council's report also warned consumers of "pay now, enjoy later" prepayment coupons, often found in food and drink retail stores with offers of price discounts.
Council chief executive Gilly Wong Fung-han said that the number of complaints about prepaid coupons had shot up in recent years, from 165 in 2011, to 1,433 in 2012 - of which about 1,000 complaints were against a single item - and 402 in 2013.