You point at your desired potion

"The red potion...?", the man asks.
"Well this potion will make so you won't gain any weight, but only for a certan amount of time!"

With the unhealthy diet you have, this could REALLY come in handy! You take out your wallet, but you are interrupted by the masked man.

"Oh, you silly girl! I am not selling these... they're FREE!"
"you see... I am a alchemist... I brewed these marvelous potions myself. I need someone to test these potions for me..."

Free? Oh, this sounds like a win-win situation... you don't know why he needs you to test it, ans he clearly know the result

"If you test this for me,you should come back tomorrow, and I shall pay you!"
"All you need to do is to drink this, and tell me if you feel any side effects!"

Ah, side effects... probably couldnt be that bad. It's easy money. You can't turn that down...
You nod, and he gives you the potion. You walk away from the alley, and towards your awesome car.

Next: https://www.furaffinity.net/view/13117272/