Sorry, I'm talking rubbish!
Silly me! What twaddle!
Oh dear! I do talk nonsense sometimes, don't I?
Just ignore me. I am clearly being stupid today.
Oh what a brainless person I can be sometimes!
I think I'd better go home before I make even more of an idiot of myself.

I'm thinking "Forget that!" or "Ignore what I just said!" would be 'clean' possibilities.

Oh, for crying out loud. That's not right at all.
Oh, good grief. What was I thinking?
Oh, no, of course not. How stupid/silly of me.
Oh, forget it, I have no idea why I just said that.
No, that's ridiculous/crazy, of course that won't work.
No, wait, that was all a total crock, I take it back.
No, actually that's total garbage. Sorry, just ignore me.
Never mind, don't listen to me, I don't have a clue.
Sorry, I don't have the foggiest idea what I'm talking about.
What a pinhead/moron / What an idiot / etc.

Basically, 'rubbish' is BE and 'garbage' is AE, and 'nonsense' is somewhat more formal. But if you don't have to be too literal, there are lots of options. (-:

For 'dummes Zeug reden,' you might also find something here:

related discussion: to shoot the breeze - einfach so daherreden

and just 'avin' a larf!

DW's examples are for when you were INTENTIONALLY spouting garbage, whereas "Ach Quatsch ich rede dummes Zeug" indicates that you've just stopped yourself mid-garbage because you suddenly realized you weren't making sense.

@hm--us: OT/ Can you shed any light here?
related discussion: Part of 'So long, Marianne'
/OT

@LaraUS: True, good point, although I'd contest the assertion that "Ach Quatsch ich rede dummes Zeug" always indicates that. My daughter almost always says that after intentionally leading us up the garden path, and my wife says it too sometimes. More often after intentioanlly doing so than otherwise. They may or may not be typical, of course... (as you know ;-) )

I guess it depends on the intonation more than the wording in German.

Anyway, 6:03 to 23:09 is LONG ENOUGHin the office for a Friday, don't you think?

My wife confirmed that they are not typical and LaraUS is right in #7, even though -- as far as they are concerned -- I was also right.