Although many Americans can't start their day without a cup of coffee or tea, die-hard fans of diet sodas claim there's no substitute.
Elton John, Victoria Beckham and even former president Bill Clinton admit to being hooked on Diet Coke, and they're not alone.
For many, diet sodas fulfill a craving for sweets while giving drinkers a jolt of caffeine with few or zero calories.
Amanda Sanchez, a 29-year-old working mother of two, is a self-professed Diet Coke junkie.
"It's my water. It keeps me going. It's the fluid that keeps me alive," Sanchez said. "I really think I am addicted. I really think it would be very hard for me to stop."
She drinks more than a case of Diet Coke a day, or 12 cans, almost one for every hour she is awake.
"It's her main staple. I consider it a food group in our house," said her husband, Henry Sanchez.
She drinks it at home and at work.
"You hear the popping the top," her co-worker Elizabeth Perkins said. "You know when Amanda shows up to work. You can hear it in the Coke."
Sanchez says that Diet Coke helps her make it through her day.
"I really like the fizzy of the diet soda. I really like the coldness and the taste and the sweetness," she said. "If anything goes wrong, I will just grab a diet soda and it's all better.
Diet Coke and other diet sodas are hugely popular in the United States, with consumers spending $21 billion a year on the low-calorie drinks.
While the drinks may be low in calories, they have plenty of caffeine, which can be addictive.
"People do indeed become addicted to caffeine very rapidly, and they also withdraw from caffeine very rapidly," said Dr. Harris Stratyner, an addiction specialist at Mount Sinai Medical Center. "It can make their sleep patterns disturbed. It can make them restless, wired, anxious."
There is no major study that says drinking diet sodas is bad for you, but some health experts say it may have health consequences down the road.
"There is some evidence that the acid load of soda, regular or diet, has an adverse affect on bone health," said Dr. David Katz, nutrition expert at the Yale School of Medicine. "I would be very worried that if you are drinking 12 cans a day, diet or regular, it's potentially going to do damage to your skeleton, and eventually that can be a very serious problem.
The Coca-Cola Company said it sees nothing wrong with drinking lots of Diet Coke.
"Great taste. No calories. Wholesome ingredients. How could you drink too much?" said Diana Garza, the communications director of Coca-Cola North America.
Sanchez feels perfectly healthy, but admitted that it may be time to stop.
"I'm going to cut back. I am going to stair step it. Start [at] 12, cut back to eight, then cut back to four and then try to cut back completely and replace that with water," she said. "I've never done that before. [It's] going to be a huge thing for me."