Coke

[The right way]

In the First aid field a tube of sugery stuff is squeesed into the mouth. This tube is much like a tube of icing that you buy at the store for decorating a cake and they both do the same job. I suppose coke would work but the tubes are much easier to use if the diabetic person is in a coma or is not able to swallow a fluid properly. If sitting up or standing and able, anything with a high sugar would work. You would have to be careful helping with an insulin shot, the person should be able to help as well so you know you are making the right move.
I am not positive but I think the way given by the medical side of things would be sugar no matter what and right to medical care, more checking on this is what we need here tho because things change all the time. A diabetic who is in danger of a serious sugar low should carry the tube or an icing tube with them just in case. It is the easiest to use and travels well in a purse or pocket or car even and just a good squeeze in the mouth is supposed to do it even if they can't swallow it, goes into the blood stream through the tongue I believe.
My only fear with coke itself is it is bubbly and someone with trouble already could end up having trouble with it going down and even going into the lungs so something thick or smooth would be better in my opinion.
Years ago when I was in my 20's I had a spell of passing out (three different times), never found out the truth about it after many tests but on one occasion while at work my partner called the medical guys after I decided to do the floor dive and they told him while an ambulance was on the way, to give me coffee with sugar, A bad choice I am sure but it might have done the trick, who knows, I came to anyway. All I remember is hot lumpy gritty sweet stuff being poured down my throat like wet sand as I was waking up and trying to ask "what the heck happened, why does my head feel like it hit a truck???". Can't argue about it now but hot coffee with lots of sugar would not be my first choice either. Still not sure what these passouts were all about, I saw the vision in my eyes go all black except the person or item I was actually looking at (like a background only, kind of change) and then waking up with a crack in the back of my head. No warning, nothing. and then they stopped happening altogether. Got me out of work a few times tho.