Hi I am 15 year old who works and I will say that it is going to be hard to find a job at a big establishment as you work under children’s rules. I.e you can’t work long hours, after 4.5hr you get a break and you can’t be on a payroll. You also can do certain things like use a coffee machine or knives.
So I would steer away from big corporations and try small cafes and things first however by all means ask because the worst they can do is say no. Also I would also mention that there is no minimum wage for 14 year old so watch out for people taking advantage.
Tbh. I don’t think you are going to find a job that will pay in cash.