Cats drinking milk is a commonly held perception, but dairy products don't always agree with their digestive systems. The only reason people think of this was from the days before cat food when people fed cats right out of their refrigerator. There is special milk made for cats in your local pet store that is better for them.
Chocolate is supposed to be very bad for cats because of the theobromine and the caffeine. Other things with caffeine, including tea and coffee are bad as well.
Oddly enough, you should not give your cat lots of fish either. It's not poisonous, but it could lead to malnutrition in your cat.
Finally, do not let your cat drink anything with alcohol in it.
Cats are among the most curious animals and they tend to taste everything they find, caution being almost nonexistent. Even it is more suspicious than a dog, a cat is constantly exposed to risks, due to its qualities tosily reach places, that are inaccessible to other animals.
For instance, if they are bored, cats have the habit of chewing the plants that are found in the apartment, some of them producing various intoxications.
Apparently harmless, table salt can become toxic, if it exceeds a certain threshold and there is no water around. So if we give to our cat very salty food, water is the best antidot. Otherwise, it can occure diarrhea, convulsions, ataxia and anxiety.