A cheap pair of earbuds.

I lose and break them all the time, so I don't buy nice ones, and I don't get around to replacing them until I'm really desperate. I think it's close to that time, because I tried to think of something that would make me happy right now, and my first thought was music

IDK, probably go to the import store near my house and pick up some white rabbit milk candies to start. Then spend the rest on cheap snacks at the dollar store. However much it left, if it's just change, probably throw downtown where I live because I can guarantee some homeless drug addict might scramble to pick it up.

Ice cream for the wife and kids :)

Buy a kebab. Really not much you can do with $15.

Go somewhere further away by a coach bus. Or maybe a 1st class train ticket (as a student I can travel in 2nd class for free in most trains).

I like travelling. Just sitting in a bus/train doing nothing.

Trying out a shooter I never played that looks good. From now me taking a look at my wishlist, could be a random one between SUPERHOT, Diabotical Rogue, ULTRAKILL, Turbo Overkill,

With the remaining money grab some snacks.

10 Robux

Invest it

Save it until I can afford to spend it in a 3rd world country for at least 5x the return value

I'd spend it teaching people how to use a dollar sign

I would buy 15 bullets and see how many fit in my head.