Excuse me, what are the hotel's regulations on buying drinks?

There are no specific rules, just find the cheaper one. Larger hotels like that may consider quality problems, but small and medium-sized hotels will not. If you want to be an agent, you can start with some western restaurants, bars and water bars. I have been in the western food industry for a long time, and apple vinegar is accepted by foreigners faster than China people, so it is rarely sold in Chinese restaurants.