Buy drinks with sugar in a non-can format. If there's a bunch of cans, plus 2 plastic bottles, that's easily distinguishable.
What this avoids is having to try each can in turn to see if it has a rubber band or string or whatever. The instant you grab something, it's obvious if it's a can or bottle, which is important when you're having a medical emergency, ...
Just a simple thought: you could use a little piece of string tied to the hole in the tab to mark the odd ones out (that's less work than marking 90% of the cans). Like this (it's Friday afternoon, so I have no soda can available):
My wife is not blind, but I have run this identical scenario with her in case I have a heart attack or stroke or something.
Step 1: Put the car into neutral. Since the engine is still running, brakes and electronics will still work. Both our cars have typical automatic gear shifts and will go into neutral by simply pushing it forward out of drive.
Step 2: ...
Low blood sugar (hypoglycemia) for an insulin dependent diabetes is a medical emergency, consuming sugar is a matter of life and death.
The cans containing sugar should be marked, if the marking comes off, accidentally consuming a sugar beverage instead of diet, is much less life threatening
Place a rubber band around the center of the sugar soda cans. ...
There are many good answers here. I'd use that old lifehacks fallback: duct tape. Just wrap a band of duct tape around the middle of every soda that includes sugar. It will be an easy, tactile way to identify cans containing sugar.
Is it beyond the realms of possibility to just put the sugar containing drinks cans inside a plastic sandwich bag, ziplock, whatever and tie the top? 2 cans in plastic bags in the cooler doesn't matter if you can see or read braille or not. Foolproof and safe, and you will be able to recycle/reuse existing plastic bags and thus save a dolphin.
Braille labels are available — some of them are made specifically for cans.
A blind person without the help of a sighted person can take advantage of the difference in density between diet and sugary drinks. Diet sodas cans float in water; regular soda cans sink.
Honda's with Lane Keep Assist Systems also have systems called road departure prevention. Which after LKAS has turned off will attempt to keep you in the lane as you leave it, and depending on how fast you are leaving the lane will brake the car as well.
Source: I worked for a supplier of driver assistance systems for Honda.
In addition to the other fine answers here, I wanted to point out another potentially valuable tool that you might have available.
My vehicle (a GM) is equipped with OnStar, and one of the available functions it provides is the ability to remotely slow down the vehicle. The intended use case is to end high-speed pursuits of stolen vehicles. OnStar ...
Put the sugary cans in a plastic tub inside the cooler.
A huge benefit to this method is that the person doesn't have to feel the cans one by one. Just find the tub. You need to use an appropriate shape to reduce the risk of cans rolling in or out.
You can stick a label onto the top/side of the tub to remind others not to put other drinks in ...
Requiring no additional resources, and better than @niels-nielsen's suggestion (which risks breaking the tab or seal by pulling):
Rotate the tab 90 degrees for the desired type of drinks. The top has a recess in which the tab sits that a blind person can use as the reference.
Note: if a blind person can read braille, they can easily detect the recess and ...
when planning for emergencies try to make the protocol very easy (were the ones with a thread sugar free or with sugar?) ...
Some totally crazy ideas:
get two coolers! one for the blind person close to them, so it is easy to find.
all of you drink sugary drinks, no confusion, all are happy (sugar replacements are allegedly cancer inducing anyway)
Ideally, you'd use a device that can make Braille labels. As an alternative, there are devices that make embossed labels - but you'd have to agree on what encoding to use (e.g. 3 dots for drinks with sugar, one dot for no sugar).
In addition to other answers.
I would like to point that if your parking brake is not accessible by passenger, then you can brake either by switching to lower gear, or even to rear gear. Of course switching gear on high speed can damage transmission, but in life/death situations its small price.
I think nobody thinks about switching to rear gear because ...