First I would ask, Why are you creating two characters with the same name? It creates the problem that you are asking about: how do you distinguish them? Is there some reason why both characters must have the same name? Is the name significant in some way that the story wouldn't work if one of them had a different name?
If your answer is just, "I thought ...
You could have a look at how this is done in Sarah Pinsker's story "And Then There Were (N-One)" which has (almost) all the characters with the same name. They can be identified by different things about them such as where they live, their job, their physical characteristics....
Try choosing something that reflects the attitude of the narrative voice and establish a difference as soon as it's needed. For example:
Slutty Susan took a long vape hit and Susi queen bee just rolled her eyes and shut the door. From then on, Susi-q kept the upper hand.
This answer is inspired by the novel "The Gone Away World" by Nick Harkaway. If you haven't read this book, I highly recommend you do so, not only is it an excellent read, it might also give you some ideas of how to deal with your situation.
Also, if you haven't read The Gone Away World, major spoilers ahead, as my suggestion here is effectively the entire ...
If you’ve made sure beforehand that the reader understands that two different Johns are present, calling each one simply “John” could be fun. To make sure the reader knows which is which, include indirect information. Examples below.
If one John just finished a long trip, while the other just got rest :
— Hello, sir, said John tiredly.
— Hi, John ...
Maybe you could name them as John1 and John2:
"Hi, I'm John." John1 said.
"No, I'm John." John2 said.
Or maybe First John and Second John.
"Hi, I'm John." First John said.
"No, I'm John." Second John said.
And maybe when they are talking to each other they start using nick names for each other, like "Johnny come lately", "Johnny boy", "Red John", "...
Any time you get two or more people in a group (or a family) with the same name, they are almost immediately given a nickname or some extra appellation so everyone knows who is being talked about.
As an example which I used in a different answer:
Take an Italian neighborhood with five friends all named Joseph. One will go by Joey D (for his last name). ...
John specifically has a wide array of cross-cultural appeal, originating from Hebrew and having a variant in just about every European and Near Easter language family. It's super easy to solve your problem:
They aren't spelled the same way
John in English has a varient spelling of Jon, most famously used by the owner of Garfield in the comic and various ...
You could give subtle mannerisms which are unique to each one (such as over-blinking, or a stutter). When they, have those mannerisms play out so that the reader knows which one is speaking at the time. It could be quite enjoyable for the reader to figure it out themselves (so long as it isn't hard work).
In a written medium, your readers can only identify your characters by what you give them. We cannot "see" your characters. So, if at any point in the story there's a John, and then again there's a John, they're the same John, unless you give us something else to distinguish the two Johns.
"Something else" might be a surname. It might be a nickname. It ...
We can change the writing styles.
For Eg. if we are talking about first person (with same name as second ) we can use bold letters, and when we talk about second person (with same name as first) we can use same style as given in story.