Lixisa17 It's not a bug. But it can be annoying. Making bar drinks is just one of those things' sims do autonomously among a number of others. What they do depends on the sim really. Traits, mood, likes\dislikes, what objects are available all play a role in what a sim will obsessively do. The way to control most of it is to keep the sim busy doing the things you want them to do rather than let them go idle. Also watch the queue for things that the game will add. Another way to stop most of it is to play with autonomy off or use the Game Options setting to turn off autonomy individually.
Hope this helps.
