An occasional trope in media, or in real life, is to have someone who is obviously intoxicated handed another drink and, when someone calls the server on it, they say that they gave them water instead of vodka, or a Jack and Coke without the Jack, with the implication being that they're doing the right thing by not giving the person more alcohol, but also avoiding conflict by fooling the person into thinking they're getting alcohol when they're not. Leaving aside that the effects of alcohol are sometimes as much about thinking you're drinking, it also occurred to me that, in a business situation, it could be argued that the bartender is instituting a sort of fraud on the customer by doing an extreme version of "watering the drinks". I assume that there'd be some degree of leniency if the bartender argues that they were trying to avoid harm by doing a reduced version of refusing service, and that a further method of avoiding trouble would be not charging at all for the substitute drinks (not even charging them for the soda you substituted, for example), but I could see a case still being made for a customer, or someone with them noticing the switch, claiming they are being defrauded.
So, is it legal for a bartender to switch someone to non-alcoholic drinks without telling them in the United States?