Things to do over summer instead of sitting on my phone 24/7??Watch
Exercise is probably good for you and can be enjoyable
Hobbies - if you have any go-tos then do those, and/or start out in other things to find more things your interested in and develop other skills like cooking etc (just remember you're on holiday; don't force yourself to do things you don't like for the sake of doing them, but also don't stay only doing things you know you like (sitting on your phone 24/7)
if you have nobody to see / no commitments, forget about the words 'sleep schedule' and wake up super early or go to bed super late
Bake cupcakes/brownies/cookies and become a pro cake decorator, write a short story, paint something, read a really good book or listen to an audiobook, visit a new town/city with your friends, or by yourself, go on a shopping spree, redecorate/rearrange your room, watch a new film, or an old favourite, find a new series to watch, visit a crafts store and try making something, buy a journal and write in it everyday, go to a local café and take a book/your laptop, volunteer at a local charity shop, take a load of photos, edit them + make a photography Insta page, make a fanpage for your pet (if you have any), make a scrapbook and fill it with memories of you with friends/family, play an online game, explore new bands/songs on Spotify, take a self care/spa day at home, do a giant jigsaw puzzle, research deep questions, watch videos on conspiracy theories.
I used to go on private land and practice driving when I was this age so you could try that, get your parents car, find some land, get permission and practice clutch control etc
- Read books without distraction so you're brain doesn't rot
- Learn to shoot bow and arrow for the coming apocalypse. Gain hunting and sneaking skills for use against humans, should there be any kind of 'purge' scenario.
As much as people say prepare for next year in school I would probably recommend against that, summer is an opportunity to take a break from schooling and learn new things and discover new passions, there are lots of opportunities to learn new things and at your age you can afford to fail at new activities so why not try new things.