Extremely difficult to do, although I've had some success with brewing a base beer, adding root beer extracts and back-sweetening with non-fermentables (lactose and Splenda). Can't say as I'll ever bother doing it again.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk