I mean the obvious answer is think up a very boring token consequence (e.g. time out, loss of privilege) and start imposing it every time it happens, with one chance/warning to correct his tone. And/or pause all interaction until he corrects it (e.g. if he is asking for a drink you only get the drink if he asks nicely).
What happens if you do that? Because just telling him you don't like it doesn't seem to be working.
OTOH if it's happening every day I wonder is he even aware that he's doing it? Does he know the difference between speaking politely and having a tone full of attitude? Does he ever self-correct e.g. in response to a look or an "Excuse me?", does he use the same kind of speech with other adults? If you talk to him about tone, does he understand that the way you speak/the words you use can have an effect on how the person receives the message?
Is it possible that adults in the family tend to put emotion emphatically into their tone, ie, do you/your partner often speak to him (or each other, or to yourselves/inanimate objects, possibly as a joke) in an exasperated or irritable way, perhaps if his behaviour is especially annoying? Is his tone objectively rude, or does it sound rude because it sounds like the kind of language/tone an adult would use to chastise a child? I could imagine an adult, not unkindly but firmly saying e.g. "Go get your shoes, now" - is he mimicking this?
Has this come out of nowhere, or have you always generally accepted him expressing emotion using tone and only recently have started to reflect that it feels rude/think he ought to have got the hang of tone by now?
I ask the last 3 because DS2 (age 7) can be absolutely terrible for all of this and consequences have little to no effect on it, but I've come to realise it's a combination of these things. He has ADHD (possibly ASD as well) and I genuinely think a lot of the time he's completely unaware of the tone of his voice but also when he gets caught up in an emotion or righteous indignation he just loses track of everything and gets fixated on whatever he sees as not being right. He can't just drop it and leave it, he won't even hear you if you try to interject, he gets more and more worked up which makes him come across as more aggressive. It's only been recently that I've been able to try and talk to him about the effects of tone, because his attention span was so extremely short before he started medication, but we've started doing it as a game (e.g. playing shops/café) where we pretend to be very posh ladies/gentlemen and ask each other in the most exaggerated way "Oh excuse me, please, if it's not too much trouble, could you possibly, possibly, please, pretty please with sugar on top pass me a napkin? Thanks awfully, old chum. Oh you are a dear, dear friend!" Or we think of the rudest possible way to speak to each other (silly, child friendly versions of rude only) and then the other person pretends to be mock outraged or upset - which also tends to invoke hilarity. But anyway doing this kind of thing as a game tends to highlight the difference and means we can revert to a toned down version in everyday life. If you name the characters as well (e.g. Lady Ponsonby-Smythe vs Mr. Rudy Layabout, or Robin Banks) then it works as a helpful shorthand in the moment because rather than going down the correction/warning path which can just wind some kids up, you can say "Hang on, I thought I heard Mr. Layabout just now, I didn't know he was here today, I thought I was talking to Joey?" that often gets them to giggle and self-correct.
But also, DH pointed out about a year ago that when I get stressed out I used to tend to raise the tone and volume of my voice as well and I'd start chuntering away to myself stuff like "Oh my GOD! Where are my stupid shoes?? Where have I left them now? For goodness sake!!" etc. I don't mean anything aggressive by it, and probably do it as a self-deprecating exasperated humour thing but young children (especially if they are ND but really any children) don't pick up on this as funny, they just see it as either a stressful thing or a normal way to express that you are feeling angry/frustrated. So I stopped doing that because I realised it wasn't giving a very good example. The bit I find harder and I think DH does as well is that when DS is on a wind up, or starts up at you or e.g. if he starts up at his sibling, the natural response is to snap back, or get right into that "firm adult" tone, to shut it down and get him to see it's unacceptable - but it doesn't really work, it might get him to stop talking but it rarely ever gets him to drop the attitude, he still feels hard done by, sometimes it just raises the overall volume of the conversation and fuels an explosion - I think what it's actually modelling to DS is that when you're unhappy with someone, it's acceptable to raise your voice at them, which is not the message we are intending at all. So I have been trying really hard to consciously stop doing this. However that's much harder to do. The best thing I've found for this is to have a go-to replacement, so what's working for me at the moment is to use words like hang on/hold on, just a sec, or stop/pause/rewind - this tends to insert enough space into the conversation that I can use a calmer/kinder tone to make my own request or point out that the way he's speaking is unkind, rather than feeling that I need to use authority in my voice to override the conversation, which he doesn't recognise as an adult-only thing and tries to use on everyone else. I can't stop other adults (e.g. at school) from using an authoritative voice around DS, but at least I can avoid doing it at home and have it as a clear expectation that we don't do that in our family.