Scatter some kindness
Get a good friend to create a plan with you to spend a day the week before your birthday to scatter some kindness.
Pick up a few inexpensive goodies at a grocery store. Maybe some fruit snacks or cookies. Drop them off at your local food shelf or a shelter. Then go somewhere for a cup of coffee or hot chocolate, and buy one for an unsuspecting person. If you happen to see a homeless person along the way, give them a dollar from each of you.
There's probably a nonprofit organization in your area that could use a couple hours of help from willing teens. Might be raking leaves, serving dinner, or just talking to an elderly person who has no visitors.
When it's your birthday, you can look back at what you did and enjoy the good feeling. It will also be like giving a gift to your friend who gets to experience this day with you.
Many years down the road when someone asks what you did for your 18th birthday, this just might be what you remember.