Energy drink Red Bull does not give drinkers the ability to party all night, research suggests.
Many people drink Red Bull with alcohol
A study of 136 clubbers revealed one in four thought mixing it with alcohol boosted their energy.
But Brazilian scientists, reporting in Alcoholism: Clinical and Experimental Research, said their tests had shown this was not the case.
A Red Bull spokeswoman said the drink was not meant to give increased energy levels when consumed with alcohol.
The team at the Federal University of Sao Paulo, asked 136 clubbers in the country about their Red Bull drinking habits.
They found that three quarters did combine the energy drink - marketed as the drink that "gives you wings" - with alcohol, because they believed it increased the stimulative effect, or lowered the depressive effect of alcohol.
Just over a third reported increased happiness, 30% euphoria, 26% said they became more extrovert and 24% reported increased vigour.
The researcher then put 14 healthy volunteers through a cycling endurance test an hour after drinking water, alcohol, Red Bull or Red Bull mixed with alcohol, over a four-week period.
The test lasted until a set heart rate was reached or the volunteer asked to stop.
An hour after the test, researchers checked the
volunteers' heart rates, blood pressure and respiratory rates.
The results showed that when Red Bull was consumed with alcohol it did not improve performance or reduce the effects of alcohol.
Report author Maria Formigoni said: "In Brazil, as in other countries, the use of energy drinks such as Red Bull is relatively common in bars and night clubs.
"Many young people use them mixed with vodka, whisky and other spirits.
"I think the main message of our study is that this kind of beverage, at least in the tested doses, does not increase people's performance in physical activities or reduce alterations induced by acute alcohol ingestion."
A spokeswoman for Red Bull said: "Red Bull is a non-alcoholic drink, however some consumers do like to mix it with different types of alcohol.
"While we do not promote Red Bull as a mixer with alcohol as this might impair its positive effects, there is also no reason why it should not, like any other drink, be mixed with alcohol as long as people do not underestimate that alcohol consumption might impair their mental and physical activities.
"Red Bull is not designed to counteract this."