This is an interview question. First you ask if there are requirements because you always test based off the requirements. After the interviewer says the testing is ad-hoc you would start with the positive functional tests, go to the negative functional tests, then to the UI, UX, stress, performance, etc., tests. The point is to show that you don't just sit around not doing anything and that you can be proactive in creating new test cases. A bit stupid in my opinion because you can have a ton of tests cases and still have shit testing, but whatever. IMHO the important things are knowing how important requirements are and that the core positive functionalities are the most important.