If you're particularly annoyed by mouth noises in your recording and you really, really want to get rid of them and you have enough patience to go through it by hand, the Repair effect is your best friend in Audacity. I suggest assigning it a keyboard shortcut or using Ctrl+R (repeat last effect used) a lot.
You find it in the Effects menu, under the Built-in section/the first part of the menu (depending on how you have it displayed). Myself, I've made Alt+Z my shortcut for it, because it's easier to remember along with Ctrl+Z for Undo.

I marked a few spots with noticeable mouth noise

When the noise is outside of a word, it's pretty simple to delete it - just do a fade in/out to whatever's next to it to make sure it doesn't sound jarring. Also, Repair helps here, too. Just apply it over the ends that are now joined.


When the noise happens on a letter, it gets a bit tricky and deleting tends to cause more problems.
You'll need to zoom in.

You can only apply the Repair effect over very short segments, so you'll have to go bit by bit until the wave is fixed. (Up to 128 samples or a few thousandths of a second - if you select too much, it will give you an error alert and do nothing, don't worry)




It doesn't always work perfectly, but it can get quite addictive (I have spent half an hour removing two seconds of phone interference from two minutes of recording - I was drunk on power and didn't care it would have been simpler to just rerecord).
You can also use it to turn an R into an L if you ever need that or, in a more practical application, to fix clipped sound waves.
Here's the portion of recording I used for the example. It's the same 17s first with mouth noise and then cleaned up
You find it in the Effects menu, under the Built-in section/the first part of the menu (depending on how you have it displayed). Myself, I've made Alt+Z my shortcut for it, because it's easier to remember along with Ctrl+Z for Undo.

I marked a few spots with noticeable mouth noise

When the noise is outside of a word, it's pretty simple to delete it - just do a fade in/out to whatever's next to it to make sure it doesn't sound jarring. Also, Repair helps here, too. Just apply it over the ends that are now joined.


When the noise happens on a letter, it gets a bit tricky and deleting tends to cause more problems.
You'll need to zoom in.

You can only apply the Repair effect over very short segments, so you'll have to go bit by bit until the wave is fixed. (Up to 128 samples or a few thousandths of a second - if you select too much, it will give you an error alert and do nothing, don't worry)




It doesn't always work perfectly, but it can get quite addictive (I have spent half an hour removing two seconds of phone interference from two minutes of recording - I was drunk on power and didn't care it would have been simpler to just rerecord).
You can also use it to turn an R into an L if you ever need that or, in a more practical application, to fix clipped sound waves.
Here's the portion of recording I used for the example. It's the same 17s first with mouth noise and then cleaned up
Also, pressing Alt while using the Draw Tool will give you a Brush Tool which you can also use to smooth out glitches and mouth noises in your recording, unfortunately, since the cursor doesn't appear in screenshots, I have no images for that.