Definitely don’t do the first option, it’s important to not have a too full bladder for too long, and to go to the bathroom regularly. Best option would be to start hydrating today, and continue to hydrate well into tomorrow. The goal should be to have a light yellow urine colour. If you are concerned about not being able to pee during the moment, drink a small water bottle (375 mL or approximately 13 US fluid ounces) a hour before you need to give the sample, and you should be good to go.