This will be divided into two sections: general summer tips and more specific b4 grade 10 tips ( like final year of IGCSE) 

General: 

Make some kind of plan and or  bucket list  ( u DONT need to tick off everything but yk it's a jumping point MUCH better than being bored all day) 

Ensure that u eat healthy, sleep properly and see friends in the summer 

Google is ur friend to help u find ideas 

I will suggest a few but this is no way a comprehensive list: 

Get into freelancing 

declutter ur stuff from school

study for the next year 

watch new shows and movies 

read new books or re-read 

attend courses/summer camp 

touch typing 

Summer b4 final year of IG: 

Revise a bit but DON'T burn yourself out 

Credit: ( below from Student Room though idk who) 

I personally would not recommend revising over the summer. The summer holiday is a great time for you to do things outside of academics and enjoy yourself, you don't want to bog yourself down to early in studying because you have a whole year of that ahead of you, and trust me when I say not having a break will lead to you burning out early, so take summer!

When you go back to school here are some tips:
1) make sure you try your best in all coursework pieces to take a little less strain off the exams.
2) make excellent notes in class to ensure you understand all the relevant course material.
3) spend 1 hour each night going over the things you learnt that day, clarifying things you didn't understand and making sure you have a complete set of notes to revise from.
4) after Christmas start thinking about where your weaknesses lie in terms of subject content, and spend some time on the weekends making sure you know these areas.( do a RAG sheet for each subject) 
5) around 2-3 months before exams begin create yourself a revision timetable and start revising all the content you have learnt over the past two years. (Be aware that 2-3 months might not work for everyone, its up to you how long you spend revising and at what times. some people will do 3 months and have one full day off a week, some people will do 1 month of cramming, its all up to you, just don't start to early for fear of burnout or boredom)

You can use tools such as ChatGPT to practice the Feynman technique on 

or do online quizzes 

or past papers 

or watch vids 

It all depends on your learning style and how confident you are in that particular topic 

As MUCH as possible avoid highlighting in your notebook and re-reading notes as a study method ( rather than a learning method)