How do guys express sympathy to other guys?

It depends on your hubby's friend's personality, cultural background and values.
If the friend is not comfortable with verbal expressions of emotions, perhaps he would be happy with a gesture. For instance, if he need time to convalesce after the surgery, maybe he'd enjoy the gift of a magazine about his favourite interests, or maybe a book - something relaxing, entertaining and easy to read.
Or maybe he'd just enjoy a visit, a gift of edibles and a catch up chat - perhaps to talk about how things went with the op/

that's easy
you mumble "sorry dude"
and punch them in the arm

Bro you ok?
Yes bro.
Good.

Once I gave a friend flowers and I got made fun of. I gave him the flowers because his cat just died and I thought they would brighten up his day so I didn't appreciate being made fun of. Cheers!

To actually know what your friend actually likes.

If you don't know him... well then you're not his friend. You're an acquaintance.

This generalization of gift ideas causes more problems than it's worth is the point. If you don't know them don't bother. If you're uncertain, then get to know them. Not just give a generally accepted gift.

I've actually knew a woman that hated flowers! Same with chocolate.

It depends on the group or culture tbh. I have friends where if we haven't seen eachother in a while we'll hug and kiss eachother on the head 🤷‍♂️ but we're all pretty open minded and have known eachother for say 15 years so it depends I suppose.

A slab of beer

Lol. Just be there. For my guy friends to just be there or call would mean a lot.
What’s the matter with him treating men like women!? We don’t want no flowers, cards, or any of that shit.

send him a 6 pack with a card wishing him well and make sure to throw in some witty insult at him. Always does the trick

most American men are very bad at emotions

Wrote the sentimental part on a check.. 🤔

We send each other porn magazines