I think I speak for all Americans (except Mike Pence) when I say: What the heck is the point of non-alcoholic beer? But it turns out to be popular in Europe as a sports drink. Which, to be fair, is no weirder than the way a lot of athletes here swear by chocolate milk.
Non-alcoholic beer is almost exactly what it sounds like: You make beer, but then you heat it to boil off most of the alcohol. Some near-beers have up to 0.5 per cent alcohol by volume, which is little enough that it's legal to sell to children.
The two drinks are similar in their semi-scientific backing: Studies funded by drink companies find benefits to beer or chocolate milk. A study funded by Erdinger Weissbrau found that marathoners who drank non-alcoholic beer had fewer colds and slightly lower concentrations of a blood marker for inflammation, compared to marathoners who drank a non-alcoholic beer whose polyphenols had been removed. (Polyphenols are natural chemicals that occur in beer, and include tannins.)
This isn't exactly convincing evidence that O'Doul's makes a good sports drink, but you're probably going to be thirsty when you finish your workout, so if you like the taste of beer, why not?