Soft drinks are included. Don't recall which brands they use. They also have fruit juices, and by the pool they've traditionally had some flavored fresh lemonades. It's easy enough to sneak in your own booze to sip from or use as mixers (outside of the restaurant, of course).
I did just notice that the inclusive menus page no longer has a listing for poolside lunch. Does anyone know if they've eliminated that? Or can you now just order poolside from the Sur House lunch menu? The poolside menu from December 2022 was definitely paired down from my previous visit, so I could see guests not being impressed by the offerings.