Can someone help me to get money for a trip?

Hello!
My name is Cam. I'm a senior in high school and I've been recommended and accepted into the American Music Abroad Program. I'm so excited because we're going to be touring Europe (mainly Austria and Germany) as well as doing the one thing in my life that gives me a name in my school and a purpose: singing! This will be the most amazing experience of my life before I go off to college and I hope that I have many more experiences as great or even greater than this trip.
The problem is, however, that I have no way of making the money to fund this trip. The amount that I'll have to pay at the end of five payments is almost $3,000! And that's not including the spending money that I'll need for souvenirs, independent lunches and the money that I need to pay for my uniform (probably another $1,500 altogether)... I don't have a job and the money that I save up is from lunch money (which I get every two weeks; $20). My dad has already paid the first $200 needed (per application fee) and I have $300 right now, so I can pay the next payment, but I need to figure out a way to make the rest of the money. I'm getting a job, but I won't make enough money to pay for the whole trip. So, some classmates that I know who went last year told me about how they wrote to companies asking for sponsorships (like Pepsi, Coca Cola, M&M Mars, etc.). Doing that could help to make things so much easier financially.
Another problem, however, is that I don't know how to write to these companies... I don't know what to say. To whomever reads this, could you give me help in developing my letter, thinking of places to send it to, and anything else that you can think of regarding obtaining money? Your help will be greatly appreciated!

Sincerely,

Cam N. <3