Depends. Where'd you buy it? From a grocery store in the hood or at a Target in the 'burbs? The latter, I've found, isn't as good.
Coke also bottle the HFCS (corn syrup) Coke Classic into bottles and many people think it's the same as Mexican Coke. It's not, it's just normal (HFCS) Coke Classic. If you find the right stores, during certain Jewish holidays, you can find American made Coca Cola Classic made with real sugar, however it often sells out on the first day.
The Mexi-Coke has and added white sticker with ingredients, which Coke adds to it so it can be imported from Mexico. American made one shave the ingredients already printed on the bottle.
It doesn't matter if you get it at the Mexican food store, or Walmart, it's all the same recipe. However, some of the Mexican stores, could be getting it from a different bottler (slightly different filtered water), and they use recycled bottles, whereas the officially imported ones always have a new bottle. From what I am seeing, the unofficial ones are getting harder and harder to find as it's easier and much cheaper to get it right from the local distributor.
10 years ago, one store here went from a bit over $1 a bottle to $2.25 a bottle for Mexi-Coke in a little over a years time, and not only was it still going up due to shipping fees, it was becoming harder and harder to get it at all. They would go months without any. And unfortunately, there isn't a Mexican food store on every other corner here like where I used to live.
is this mexican coke just coke made with real sugar?
Mexi-Coke is closer to what Coca Cola was decades ago, before New Coke, which is why the bottle doesn't say "Classic".
When Coke reformulated to New Coke it was a disaster for them, while people preferred the taste, they were angry over them changing something so iconic. When they switched back due to pressure, they didn't actually go back to the old formula like people think, they reformulated it to be cheaper to produce and used HFCS (High Fructose Corn Syrup). Which is the real reason why it's called "Classic", it's not really old Coke (Coca Cola), but instead a retro flavor. I suspect it may be a cross between old Coke and New Coke, and while I can't confirm that with any documentation, there is a difference in flavor.
Mexi-Coke not only uses real sugar, but the flavor is slightly different, it has a bit more spice to it, it's also less syrupy (and therefore a bit better for your teeth). While you can drink HFCS Coke all day and not feel full, Mexi-Coke actually will fill you up. Your stomach recognizes sugar as a food, while HFCS gets ignored. Even at an increased cost, Mexi-Coke can save you money compared to HFCS Coke simply because you will drink less of it.
Interestingly, if you spill Mexi-Coke, depending on conditions, I've seen it dry into just a sugary powder rather than a sticky goo, I always thought it was Molasses that caused the goo, but it's actually the corn syrup. I have also found warm Mexi-Coke to be MUCH more tolerable than warm HFCS Coke, warm Classic is hideous, though Pepsi is even worse when warm. I suspect flat, warm Pepsi would probably qualify as torture if used to extract information from people.