Wrong question. You are the one making the positive claim that god exists.

Why should anyone believe that?

one of the.multiple reasons is the principle of sufficient reason

But that's human bullshit.

We don't know that everything needs a cause.

We don't know that infinite regress is impossible.

And if everything needs a cause, so does god.

Denying the principle of sufficient reason would mean that you do not have a sufficient reason to know whether your knowledge is defunct or not. Thus, if we deny the principle of sufficient reason, knowledge and truth cannot exist

you do not have a sufficient reason to know whether your knowledge is defunct or not.

No, we use evidence. Observable evidence. "I think gravity exists." We experiment. We demonstrate it. We can use it to make predictions. It goes from hypothesis to knowledge even if we don't completely understand the underlying mechanics of it.

Thus, if we deny the principle of sufficient reason, knowledge and truth cannot exist

What a stupid thing to claim. I reject the PSR because there is no evidence for it. None of my other knowledge magically disappears as a result. If there was no truth, we would not be conversing right now.

You cannot hold the belief that your knowledge is valid or invalid as you lack sufficient reason to hold it.

If you deny the principle of sufficient reason, you fall into absurdism and contradiction. There's no truth as there's no sufficient reason deeming something true or false

And yes, thats the point, truth exists and thus we are conversing.

You cannot hold the belief that your knowledge is valid or invalid as you lack sufficient reason to hold it.

Wrong, I have evidence I have sensed with my senses and processed with my brain.

If you deny the principle of sufficient reason, you fall into absurdism and contradiction.

Can you demonstrate that?

There's no truth as there's no sufficient reason deeming something true or false

Wrong, there is evidence and we can repeatedly test it.

And yes, thats the point, truth exists and thus we are conversing.

Right. I believe you exist because you're here. I don't believe god exists because he's never been here.

2. Falling into absurdism like "truth does not exist" or "knowledge does not exist", one of the examples is being unable to determine if your knowledge is valid or not

"truth does not exist" or "knowledge does not exist"

I never said that. You did.

I don't reject truth or knowledge. I do reject the principal of sufficient reason, because it's unproven bullshit.

@SnoopSqueak If you reject the principle of sufficient reason, then science is over. The principle of cause and effect is at the heart of every scientific endeavor.