My solution is that, for Landians, the breathing apparatus has a mechanism that would allow to consume liquid. It can have an opening that you can attach liquid containers. It seals tightly and allows liquid to pass through a tube (possibly that can elongate towards your mouth when you attach the liquid container). Or, there can be some sort of underwater camelback system attached to the breathing apparatus.
For Aquaticans, they can just have the underwater camelback option without the breathing apparatus.
This example has even 2 compartments. It can be useful for their water intake as well.
This scuba forum has a question about underwater hydration options and the answers mention the camelback. (Although, they mention that divers don't do it normally as they just drink on the boat):
However, for the longest saltwater dive-world record, they used a camelback system:
He survived on a liquid diet of Gatorade mixed with extra protein and vitamins that was stored in a Camelback-type system, and spent a majority of his time doing the best he could to adapt to his aqua home.
Note: I'm giving this answer as it seems like Landians really need to keep the breathing apparatus on. Most of the answers don't consider that Landians have a breathing apparatus and most likely they can't just take it off for consuming something because of the circumstances.
It is not practical and even dangerous, if you try to consume something by taking off your breathing apparatus and opening your mouth (even slightly) underwater. Landians might have or need a more complicated underwater breathing system than the real-word scuba systems as Landians might travel great lengths underwater and stay longer. Thus, they can't just easily take it on/off. They might even have/need a special suit for this occasion. Additionally, they might need the camelback system not just for the wine party but for their water intake as well (assuming Landians need water, and they will stay underwater longer times or they go underwater on other occasions as well). If it wasn't the case, air chambers would be the best option.