One of the best rumors as to why Ian Fleming chose to make Bond a shaken, not stirred man was because he himself once tried a martini served that way and found it quite enjoyable. Bond's creator, Ian Fleming, was also very passionate and specific when it came to cocktails. The first drink of the Daniel Craig era is served around half an hour into Casino Royale.
Bond is a character who knows exactly what he wants and is attuned to his own tastes, so there must be a reason for his choice beyond mere whimsy. A look at what 007 drinks in Daniel Craig’s debut as James Bond. The specificity of the order has to be taken into account. Other Reddit users added their own credible theories to the discussion, including the idea that Bond prefers his drinks colder or that he orders his martinis shaken as a way of diluting poorer quality vodkas that aren't quite up to his standards.
That way, the spy can take opponents by surprise if he ever needs to think or act quickly. The shaken martini was an interesting topic of discussion in the above Reddit thread, where the original poster proposed that Bond deliberately chooses a weaker drink to keep his wits sharp while at the same time appearing more inebriated than he actually is.
