where do you want to handle them?

I need to access both server-side and client-side cookies, as I have API calls that require authentication using JWT tokens, which I store in cookies.

Assuming you use the /app dir based on the next13. In a server component you can use the cookie helper to get them from the request, although it will prevent ISR/SSG rendering and use dynamic instead. https://nextjs.org/docs/app/api-reference/functions/cookies#cookiesgetname

On the client, I am pretty sure you have to use the normal browser APIs for them like document.cookie and maybe a library like https://www.npmjs.com/package/js-cookie