time-poor, frenetic times it seems that everyone wants a slice of the energy-boosting market. And when it comes to this sector, what all the other pretenders - be they Britvic, Coca-Cola or Cadbury with its energy chocolate bar - want is to grab some market share from the king of energy brands.
As UK managing director of Red Bull, Drnek has steered his brand to an enviable position that so far no one has managed to touch. And while it would take a lot more than Britvic's purchase of Red Devil to rattle this straight-talking, unstuffy American, he's not so complacent as to ignore the potential implications.
"If Britvic proves to be a brand builder, then we're going to welcome it, because the category has been bereft of any serious competition. We'd be silly to ignore Britvic's strength in distribution and sales, but ultimately it'll be the consumer that drives the category," says Drnek.
The energy drinks category has proved to be anything but a fleeting fancy.
UK consumers drink 87 million litres of the stuff according to drinks consultancy Zenith International. Across Europe sales rose 22% in 2001 and Red Bull commands 66% volume share of the market.
Drnek is unequivocal about why so many companies are desperate to muscle in on his territory. "Everyone who looks at our business sees the margin opportunity first. Put that under the category of 'greed'. The misunderstanding of the category starts right there. The fact is you need to put a lot of that back to the consumer. We spend almost £20m, including the people we hire, on marketing and where are the other guys who spend a dime? It may look like fun, but it's a serious product."
But having sampled and clubbed its way to the top, Drnek acknowledges that Red Bull now has the harder task of maintaining growth and expanding use. His strategy is a combination of ensuring it is served correctly in the on-trade (this man can talk for hours about the optimal way of pouring any drink), encouraging older consumers to buy it as an instant pick-me-up, and making people think of it as a source of energy during other activities such as sport and driving.
The company is not interested in new product development as a way of growing sales. Drnek says it looked at possible variants of its own premium packaged spirits, but ultimately came to the conclusion that they would destroy the soul of the brand.
Red Bull is so associated with the relentlessly youthful world of clubbing that it can jar to be faced with such an enthusiastic 55-year-old brand advocate.
Age is clearly no barrier to Drnek and he's fiercely proud of the calibre of his youthful staff. "Age is a number and it's about what you do with it and the people you associate with." In fact his kids, aged five and nine, help to him young at heart. His extra years, however, have provided Drnek with a comprehensive knowledge of the drinks business.
Red Bull is just the latest in a long list of challenges in the veteran drinks marketer's portfolio. He cut his teeth first in his native US on Budweiser, moved to the wine market with a stint at Ernest & Julio Gallo and once based in the UK bought the distributor Maison Caurette. It was with the latter that he really made his mark by introducing Snapple and, more famously, the Mexican beer brand Sol to the UK market.
Constantly referred to as a "colourful character", a theme runs through all his jobs: he only works on the market-leading brand. This is no accident.
Drnek lives by the mantra presented to him on a plaque by his father: 'if you're not the lead dog, the view never changes'. This is not a man to be turned on by the prospect of selling a challenger brand; the buzz for him is in leading the pack. And while he's widely respected, one industry source says: "His attention span is limited unless he's really caught up in the idea."
There's little danger that the thrills - clearly an integral part of his life -will dry up. He maintains other business interests outside of Red Bull, among them advising a Thai wine firm. And if the combination of the drinks business and improving his golf handicap become too dull, he can always "blast his ass" in his MIG 21 fighter jet.
Drnek developed his love affair with flying in the US Air Force and the Vietnam War, and flew in the last combat mission in 1973. While he pronounces himself a conscientious objector these days, the camaraderie and adrenalin rush of battle still appeals.
As I meet him for this interview on September 11, I ask him how he feels about the prospect of another Gulf War. "Given the opportunity I'd take my MIG 21 and go join them. But I've seen it does no one any good. Emotionally I'd like to be part of it, physically I'd love to do it, it'd be cool and fun and it's a game. But there's no rationale for it."
It's going to be Red Bull, not Uncle Sam, that gives Drnek his wings these days.
1976-1981: Brand manager, Anheuser Busch US
1981-1983: US vice-president marketing, Ernest & Julio Gallo
1983-1988: European marketing director, Anheuser Busch UK
1989-1995: Owner, Maison Caurette Holdings
1996-2002: Managing director, Red Bull UK