Alcoholic drink which contains a very high level of alcohol and "does not contain any added flavoring" is commonly called a neutral spirit. Generally, any distilled alcoholic beverage of 170 US proof or higher is considered to be a neutral spirit. Most yeasts cannot reproduce when the concentration of alcohol is higher than about 18%, so that is the practical limit for the strength of fermented drinks such as wine, beer, and sake. However, some strains of yeast have been developed that can reproduce in solutions of up to 25% ABV. Shot sizes vary significantly from country to country. In the United
Caffeinated alcoholic drink of caffeine to the alcoholic drinks or to stop selling the drinks altogether. The Federal Trade Commission (FTC) also took action against the four companies, warning that their marketing tactics might violate federal law and urging them to take swift and appropriate steps to protect consumers. The day before the FDA sent out the warning letters, Phusion Projects, a five-year-old Chicago company, said it would stop putting caffeine in the drinks and put a non-caffeinated version of the drink on the market in December 2010. In a statement, the company's founders said that they still believed it was safe to