It’s certainly not a waste of time to apply without relevant experience - but of course, it would be better for your application if you did have some!
You could answer this question in a number of ways. You could leave it blank, but I always think this looks poor on application forms. If it was me, I’d put down my general work experience, but focus on describing how these experiences relate to investment banking, or how the skills and competencies I picked up from these jobs would stand me in a good position for an IB job.
Even if you’ve just worked at Pizze Hut, you’ve still worked in a team (see - [[teamwork]]), or even lead a team (see - [[leadership]]) and are likely to have solved problems (see [ [[problem solving]]).
Good luck - please let us know how your application and assessment process goes!