I don’t consider it appropriate for me as I try to generally avoid beverages that are high in simple carbs. Too easy to consume a day’s worth of calories in a single sitting. And diet versions tend to taste nasty to me. So even fruit juices are rare treats for me, and I (hopefully) take them in small volumes.
But hey that’s just me; I commit lots of other dietary indiscretions that others roll their eyes at. So do what works for you.
So is beer inappropriate for Breakfast is the next question?
When I lived in Atlanta about a quarter of the breakfast orders in the cafeteria had Coke rather than coffee or tea.
Soda is way too sweet for breakfast. I have coffee every morning. No sugar, just a little bit of cream.
I stopped drinking soda long ago. It’s chemicals.
Everything’s chemicals. Except for elements. And fundamental particles. And energy.
Sorry. Has no value and does not quench your thirst was what I should’ve said
Well hell, now we’ve got to argue about what “quench” means and “thirst” means, and so on and so forth. 
In all fairness, I have to have my mug of coffee every morning but does that quench my thirst any better? Is it better for me than soda?
I believe it is. But water is better.
Water is best.
A 12 Oz Coke has 10 teaspoons of sugar.
I rarely see people add more than 2 teaspoons of sugar in coffee. Yes there are exceptions and you will occasionally see someone add a lot of sugar.
I gave up my daily soda over 15 years ago. I’ll drink one every now and then. A six pack easily lasts a month.
A few years ago, I was in line at McDonald’s; the guy in front of me ordered two coffees: one with 12 sugars, and one with cream and 10 sugars. 
Let me pour you a few drops of coffee with that bowl of sugar. 
I drank mine black for a long time. I started adding creamer a few years ago. It’s easier on my stomach and avoids acid reflux.
I like Kris Kristofferson’s take:
Well, I woke up Sunday morning
With no way to hold my head that didn’t hurt
And the beer I had for breakfast wasn’t bad
So I had one more for dessert
One of my vacation rituals is to have a beer with/for breakfast.
It’s made with grain! It’s just like a bowl of cereal. nods
Actually I had a breakfast stout for lunch. That would be good for breakfast too.
As a kid, I couldn’t imagine being allowed to drink soda for breakfast. Orange juice would have been perfectly acceptable but not a Coca-Cola. It’s kind of odd how we divide up foods sometimes. I remember when bacon was strictly a breakfast item and it wasn’t an option even at most burger places. I often have a diet Dr. Pepper in the morning.
Beer is only a Breakfast for Champions.
I drink Diet Coke any time…almost. Need to stop the caffeine by early afternoon or I may not be able to get to sleep. I like coffee but I’m too lazy to make it. If we go out for breakfast, coffee it is.
Me, I get my caffeine from strong drip coffee in the morning. Sody Pop in the ay-emm? Pffft, that’s for teenagers.
Then some Diet Coke in the afternoon if I’m lagging. If it’s noon and I realize “Crap, I didn’t have any coffee today!” I’ll grab anything. My ADD gets out of hand without any caffeine.
Just before I saw this thread, I was biking and saw a huge McDonald’s billboard. Said something like “A Bubbly Breakfast”. Big photo of Egg McMuffin, hashbrowns… and a glass* of Coke™.
*(Yes, it was glass. With clear prop ice cubes and perfectly-placed bubbles. Umm, which upscale Mickey D’s can I get that at?)