Suits have been brought against AB InBev for watering down Bud Lite. See "Budweiser Sued for Watering Down Its Beer".
If true, this is another case of proponents of free markets not really believing in free markets. The free market principle in question here is that both buyer and seller should have sufficient information to make a decision. If AB InBev is indeed watering its beer to an alcohol content less than on the label, that is not only hiding information from the consumer but providing false information.
HOWEVER, in an interview by CNBC, plaintiff attorney Josh Boxer can only cite claims by former employees, not by independent testing.
Who do you believe? Who can you believe? All I can say is that I admire the tenacity of the CNBC on-camera journalists for trying to get a straight answer from Boxer.
Generally, one can believe that "liberal" NPR. They had tests performed and found that the beers in question did have the alcohol level stated on the can. See "Budweiser May Seem Watery, But It Tests At Full Strength, Lab Says".
My own guess is that Bud tastes watery is that it does not contain the amount of hops that craft beers contain.