In the midst of a massively over-scheduled month from hell, my car (which I absolutely need for work/school/etc.) needs to go to the mechanic for at least a week. A friend is very kindly lending me her car. My question: how do I thank her? I have no time to do anything thoughtful (wash it, detail it, etc.), but I'm so appreciative. I'm happy to spend some money for this, but on what?