Create a mixture of various looking drinks in different shaped glasses like the goblets you have around your store. And each drink has a special effect. For example a goth club could have drinks such as 'green fairy' makes small green faries buzz around you, 'crypt martini' creates fog around you, 'bloodwyne' makes blood drip from your mouth and have red mist at your feet and so on. While the drinks also give you the drinking animation as well. These drinks/effect last for 10 or 15mins then the drink/effect self deletes. And if the person wants another has to buy it from the bar.
I came up with this idea as all clubs, bar, RP taverns, etc unless are in the middle of a mall and receiving rent/ad space fees, loose money. The difference between ta RL club and SL is you cant drink, per se, in SL and thats 90% of a bars/clubs income in RL. Since this is all virtual theres no such need here. However with this concept theres some level of emulating that of the RL counter part. As your drink gets 'used up' like in RL after a bit. The bar can charge like 5 or 10L a drink and given enough folks prob wont be enough to pay the bills still but will at least be something to offset them. And with cool, orginial effects gives the people reason to buy them and they are also not costly so odds are you will get repeat customers trying several of them out and 'drinking' the ones they like on a regular basis.
And as a designer you could also sell updates to the idea having the bar sell additonal types of drinks, or other types of related items. So for you its not just a one time sale but the potential of having buyers come back and purchase more for their taverns and clubs. Different drinks for diffeent types of places. Goth clubs, modern dance bars, strip clubs, etc could all have their own bundle of 'drinks' to be sold for example.
Anyways I wanted to pass this idea by the folks here as to what you thought of the feasibility of creating/scripting something like this in SL? If this is something you would be interested in making I have no issue with you taking this concept and running with it. Sell it in your store or what not. All I ask is a free mod/copy version when you are done

If you need more ideas on this concept please do contact me inworld.