It could be something as simple as a maid dipping in to the beverages in the mini-bars, and then replacing the fluids with something off her cleaning cart.
I am not too confident that the local LEO are spending much time investigating.
also posted in another thread:
Many years ago my wife and I took an extended vacation in the Caribbeans. When visiting several grocery stores, we noticed that every glass/plastic bottle and jar had been opened, some of the contents removed and something added back to make the bottle/jar appear full again. We mentioned it to the staff (locals) and they laughed and said its the way its always been done. Out of curiosity, the wife and I spent 20 minutes searching the shelves without finding a single sealed container. We each bought a bottle of orange crush soda and left the store. Once outside in the sunlight, we could see foreign matter swirling around in the soda bottles. We poured them on the ground and left. Neither my wife or I got sick because we followed a strict diet. We ate fresh fruit mostly oranges. We bought fresh fish from local fishermen, we boiled all of our drinking water. No local alcohol, no store purchases, no eating out at local spots.