Turn it into a roll of quarters and fuck myself

Buy some games on discount. I can easily get Fallout 4, or about 7-10 other games on steep discount. PC gaming is the best.

Probably pay for whatever activity I can afford with 15$ to spend time with my partner. Love her to bits and enjoy every minute I spend with her.

Donate it to a good cause.

15 $1 dollar coins stashed around the house for me to stumble upon later.

Taco Bell most likely.

Minecraft is on sale

I don't think I'd be happy if all my savings were reduced to $15.

Tacos

There's an independent coffee shop in the park by me, so a cappuccino, a big slice of carrot cake and just enough change for a lottery ticket.

Literally? Buy some heroin.

Aftermath might not be so good though.

Buy a mini Blåhaj :3

What a cool question, actually.

In my current situation? Probably a coffee date with someone new.

In a hypothetical "blank slate" scenario? Some easy way to play music. An mp3 player or something among those lines.

Alternatively - I could absolutely purchase a used dumb phone for that amount of money, as well as free calls within network for a year (in my country).

Good chocolate.