Some 59% of 18 to 30-year-olds admit to prioritising this type of "yolo" (you only live once) spending over saving or investing, peer-to-peer lending website RateSetter found.
Just over one in four (26%) people surveyed said they spend every penny they make, saving nothing.
With house prices having surged in recent years, many in this age group appeared to have given up on owning their own home. More than one in three (35%) could not imagine ever being a home owner unless they inherited a property.
And 69% of young Britons had made no financial plans for their retirement, despite 47% being worried about their later years.
The most popular regular outgoings for under-30s included takeaways, meals out, clothing, TV streaming services, coffee shop visits and luxury cosmetics.
Those who did put money away tended to be doing so to fund a holiday abroad, the survey found.
Rhydian Lewis, RateSetter's founder and chief executive, said: "With interest rates languishing at historical lows for several years and recently cut even closer to zero, it is all the more important for young people to ensure that they get on top of their finances."
Around 1,000 young adults took part in the survey.