“A ceramic ‘jar’ that I found behind the couch of a furnished rental I’m staying in this weekend.”
Answer: "It’s an old ceramic hot water bottle. If the seal is still good, it will hold a full standard kettle worth of water. Stick it on the floor with a blanket tucked around it and around your feet, and it’s the best feeling."
Could it be the picture is upside-down?
"Tastes like lime..." I'm more concerned that the person would taste something that they don't know what it is (the answer is probably correct but still...)