Most people here are going down sensible quick routes. I don't know but maybe you have a hobby that could be useful and pay. For example, enter a writing competition for a poem with a prize money of $300. Might work...
what I do, is chores... yes I know CHORES. but I make at least 50 to 60 dollars a week. and by the way chores isn't a job, they are something your going to have to do whether you like it or not for the rest of your life. :P
but if you need some serious money... like from what you say 200-300 dollars. you'll need to get a job.. like a literal job, working somewhere.
I think someone mentioned trying to use a hobby or something you are skilled at. I teach drum lessons during the school year, I only work one day a week for around 3 hours and make around 500-800 a quarter( 9 weeks). You just gotta kind of look around for what is out there. For a while I went to this local auction and bought golf bags, I got them cheap there and then sold them on craigslist and made a pretty good profit. You need to be a self starter and be innovative, it's kind of like starting your own little business. I know there was a kid in our neighborhood who would put out your garbage cans, and take them back inside for people, if you think charging just $2 per house per week, there is at least 50 houses in my neighborhood, and I think most people would go for that. So that's 100 dollars a week for doing just a few hours of work 1 day a week.
you can try a retail store. from my experience they hire fast and often (I work at one) but you're going to hate your job lol...
my friend once worked as a telemarketer (he always called it "telesurvey"... haha). anyways he said they are always hiring because everyone is always quitting. there's a machine that automatically calls people and you have to give them a survey. you're going to hate it and people are going to hate you but if you only work there for a short while like my friend did, it probably won't be too bad.
From the looks of it you're going to buy weed... joking, but the concept of MAKING 300 dollars would imply some need for a JOB (formal or informal). What you could do is go on craigslist and post that you're willing to mow lawns around your city and you could make it pretty quickly off that considering they will also compensate you for gas.
If you looking for minimum wage, you will get in easy as long as you are confidant in your interview. I recommend finding a job that you work for the city, my first job for instance was at a library shelving books, did that for almost 2 years and it paid well 7.5 dollars an hour and was a very clean and quiet place to work, fast food is just too crappy for me lol.
But in reality? I don't know if it's possible over there, but over here, you see some people driving around picking up peaces of metal and taking it to the scrap metal processor. You can get quite a bit of money from copper