What counts as "water" is undefined, and therefore up to the DM.
The spell component for create or destroy water is "a drop of water". Water isn't strictly defined anywhere in the rules, leaving it up to the standard English definition of the word. The DM has to interpret any remaining ambiguity.
The rules don't say anything about how pure the water has to be. Salt water might count as water, as may dirty water. Saliva is 99.5% water, and probably more pure than some water sources you'd find in a dungeon.
Urine is over 90% water, but many people would consider it not water due to its lack of potability. Blood would probably not be considered water, even though it contains 92% water and is described by Wikipedia as "essentially an aqueous solution", or water with stuff dissolved in it; likewise potions, beer, or other liquids defined by their difference from water.
The exact definition of water is, however, entirely up to the DM's opinion. The DM may feel generous or strict depending on the circumstances.