Let's say I have build an application in tkinter on my personal laptop and I have distributed the .exe of it to my friends in different parts of the world. Now, I want to add some features in that application for which I wrote some extra lines of code on that same .py file whose .exe I sent earlier. How can I push the updates to all my friends who are using that app without having to send them .exe file everytime I update the code?
Any answers to this questions won't specifically relate to python or tkinter since you are distributing an exe.
Here is how this might work in high level terms.

You upload a new version of your exe to a web server
When your friends open their version of the program, it or another smaller program, will
check the website to see if there is a newer version of the program available
If there it it will prompt them to update the software if they want
If they click yes, your program will close and the updater program will fetch the latest exe from your website and copy it over the top of the existing program

So for this application, you need a webserver where you can store the exe files of the different versions and will respond to requests to tell the program what the latest version available is
You also need another program which will handle the download and copying of the files to the correct locations
As you're no doubt aware, there are plenty of examples of this occurring on "App Stores"
How to push updates in a tkinter application