How do I reference letters when explaining my characters' accents?

Sorry if the question is confusing. Didn't know how to phrase it 100% right. Basically, I wanna write in my novel something like:

He had a thick accent on his Hs.

How do I write that? That the character has a thick accent on the letter H. Should I write 'H's, 'Hs', Hs, Hs, or something different? And please don't change the format of the sentence, nor turn the "H" into singular.

Solution 1:

Let's find out.

The Chicago Manual of Style, section 7.15, says this:

Capital letters used as words... usually form the plural by adding s. To aid comprehension, lowercase letters form the plural with an apostrophe and an s (compare “two as in llama” with “two a’s in llama”).

And it give the following example:

the three Rs

So, if you must write your sentence like that, use "Hs."

Solution 2:

I prefer Hs or Hs. Straightforward and not excessive. You do not use an apostrophe to make a plural.

I have seen people try to write out the letter, like "aitches," but that's hard for me to read.

Solution 3:

Alternative path: instead of saying which letters were accented, give an example of a word which is altered.

He had a thick accent, making his "house" into an "'ouse".

This only works when the accented sound can be represented in English text, of course (so no Germanic "ch" sounds).