If I was in desperate need I'd work 7 days a week, 12 hours a day, and do all sorts of questionable shit. Including those random medical tests.
Haha seriously? no way I would ever even consider taking part in paid clinical trials to get out of a money jam, the moment you sign that consent form you basically turn into a lab rat
Plus you could end up with health complications costing you even more money. You'd be better off working your ass off with 2 jobs for 18 hours a day.