On all our boats we include complimentary drinks and snacks. We have water, soft drinks like cola and fanta, beer and cava (Spanish sparkling wine).
We don’t really count how many drinks we included per person, it is limited mainly by the size of the on board refrigerator. The bigger the boat, the more variety and quantity you can expect.
We never had a customer complain about the lack of drinks, however an open bar should not be expected as our trips are nice and relaxing luxury experience, not a drink-all-you-can booze ride with cheap alcohol. For this kind of experience you will need to look elsewhere.