Question: What `съедобный` is to food, `__________` is to drinks.

Of course, one can say `которую можно пить`, and there's the word `питьевой`, but both are not quite equivalent in meaning and usage to the aforementioned `съедобный`. Any ideas?

Answer: 
The word *съедобный* has two meanings. One is that an item is edible. Another one is that it's tasty, and is used only in spoken language.

With liquids, for the first meaning, the technical word is *пищевой*, meaning 'suitable for consuming as a food'. For example *цистерны, бутылки для пищевых жидкостей* (GOST terms). However this word is rarely used in daily life, since it's usually clear for all liquids except for water if they are drinkable or not (fuel and milk for example), so one doesn't need an additional adjective. For water, since one should clearly distinguish drinking and technical water, the word *питьевой* (meaning literally 'drinking') is usually used. Obviously, milk for example can be spoiled and not drinkable. I think there is no single word to convey this meaning in Russian (nor actually in English).

There is no word for the second meaning for liquids, as far as I know.
In my opinion, `cъедобный` - is the best choise in your case. But also you can try `пьющийся`