Here are some examples:
* "Ang prutas ay mapakla." (The fruit is sour.)
* "Ang lasa ng suka ay mapakla." (The taste of vinegar is sour.)
* "Ang mukha niya ay mapakla." (Her face is sour/tart.) - This can also mean she looks unhappy or annoyed.
Therefore, the best translation of "mapakla" will depend on the specific situation and the intended meaning.