Hello!
If you go to "Extract tuning" there's the bar's Order drink interaction "bar_PushOrderDrink".
All the drinks you can order at the bar will be under "<L n="recipes">" (in the interaction's XML).
I tried adding the coffee tuning "<T>139404<!--recipe_Drink_MarketStalls_Coffee--></T>" in the recipe list.
I does appear in game when you try to order it at the bar, but the bartender won't serve it.
The drinks served at the bars and the ones you purchase from food stalls are different.
At the bar, the bartender will make the drink and then serve it to you. At the food stall they will just serve it to you.
So just adding the coffee to the bar's lists of drinks won't work (I guess).
I think if you really want to purchase from the bar, you'd probably have to clone one of the bars drinks' recipes and create a custom coffee recipe.
Or you can clone a food stall, or another object that works the same way (like the school cafeteria from High School expansion), add the coffee tuning to the object's "PushOrder"'s interaction (give it a new tuning id). Then change the stall's/cafeteria's mesh to the bar's mesh.
Sorry if this is confusing.
Maybe someone else has a better idea.
Anyway, good luck to you.
