Choices are limited. I find Stevia works really well, but rarely use it. In coffee I use 35% cream and - if I can get it - Kiss My Keto's chocolate MCT oil powder. This stuff rocks!
Stevia can have an aftertaste which some people find bitter; it probably has to do with the solvents used to distill the sweetener out of the leaf of the plant, or with the other additives most manufacturers insist on adding to stevia. The Sweetleaf brand in Canada has no aftertaste and is made with stevia only. Most stevia products contain sugar alcohols (Erythritol is typical, & fine) or malitol. But many contain Dextrose, Sucrose &/or Maltose. You have to search the label for the fine print, as they're marketed as stevia products. This is EVIL! In Canada this has been done by sugar manufacturers to white-wash their sugar: they add stevia to sugar and then label the product "Stevia." I thought this was illegal. Read the fine print on everything: you'd be amazed what you find.
"Natural sugars" is no good. Obviously dextrose & sucrose are not helpful if you're diabetic or on a ketogenic diet. But the health food industry has many players happy to shove fructose on you. All the supposedly "good" natural sugars are going to spike your insulin levels. This means any fruit sugar, including coconut sugar, maple syrup and agave. Honestly, I can't comment about Monk Fruit sugar but Maria Emmerich seems to allow it for cooking so it must not be fructose. I still avoid it. Honey is definitely out: its a mix of sucrose & glucose. Fructose is especially problematic: the brain & body use glucose, and you liver converts most usable sugars to glucose either immediately or over time. Sucrose, for example. Fructose, however, is garbage: your liver can't use it and can't convert it, so apparently it is stored as fat, much of it in the liver itself - where it stays as any fat we can't break down we can't metabolize later, no matter how hard we work at it. Fructose storage in the liver is why obesity appears to occur in combination with fatty liver disease. All the high-fructose corn syrup that is the mainstay of the soda pop industry is therefore poison, and should, IMHO, be regarded as such. Not good for anyone, not just those of us on keto or who have diabetes.
BTW, any chemical name ending in "-ose" is a sugar, and there are many of them. Lactose, for example, is a sugar found in milk & dairy products, one of many, which is why dairy can cause insulin spikes for diabetics and is a problem for some users of the keto diet. Dairy appears to affect some more than others, but apparently not all.
Sugar alcohols are OK, but may come with issues. Erythritol is Emmerich's go-to for many recipes as it seems to be less likely to impart a bitter aftertaste than stevia does when used for cooking. My own experience with stevia (Sweetleaf's, at least) is that it works fine for cooking. The other major sugar alcohol is Malitol. Invented in Finland it is derived from Birch sap or wood (interesting, that, as Maple sap is definitely fructose). The claim is that it has no impact on insulin, and you can definitely cook with it, but many people will apparently find there's a definite tolerance level: past that and you get "gastro-intestinal outcomes" (diarrhea). I'll pass.
I tried using sucralose for cooking early on, but found that it didn't perform nearly as well as the manufacturer claimed (I could never make recipes work), and it appeared to spike my insulin levels despite what was claimed. Since I've have avoided it, and I've discovered more recently that there's very sound research indicating that sucralose and aspartame are implicated in the rise of obesity. So for me, they're out.
I do find that going Keto vastly reduces your need for sweetness. What cravings I get are usually satisfied by the additional fat in the diet. Using sugar replacements much - or especially using sugar - seems to me to be a work-around that benefits no one except the sugar industry.
I've learned a lot about Keto, but confess I know a lot less about diabetes. And I am certainly no medical expert or practitioner. The Keto diet appears to be enough to enable many T2 diabetics to reverse the disease, treating it without insulin. And while for T1D it didn't work long-term (patients eventually died anyhow), it is essentially what was used before insulin was discovered: they used starvation diets, which induce ketosis. If you are on the diet you'll always have a baseline level of glucose in your system even if you succeed in ingesting none of it (**** tough to do in today's world: the stuff is everywhere). Your body apparently converts proteins you eat, or if necessary, the proteins in your body, into glucose to maintain the low level necessary. Something like ~2 mM, I believe. Beyond the baseline required you can use ketones to do everything normally done by glucose, which will reduce your need for insulin enormously.
That in mind, perhaps someone who know more about this than me could discuss for us whether a keto diet could benefit T1 diabetics, obviously in conjunction with insulin. Seems to me reducing your sugar levels would be a good thing. Ingesting sugar like a "normal" person then constantly trying to balance sugars ingested with administered insulin seems like a losing battle to me, a mug's game, and I don't wonder that eventually the roller coaster ride that results wears out organs & results in a shortened lifespan.
That said, I gather that ketoacidosis is a very real risk for T1 Diabetics, so suspect that while a non-diabetic can regulate glucose levels required and function fine even with high ketone levels in the blood (something we strive for on the keto diet), this appears to be something the regulatory systems in a T1 diabetic's body can't handle. That's speculation. I'd love to understand this better, and haven't yet found a cogent answer in the literature. I haven't got anywhere asking medical doctors or nurses about this: they get no nutritional education by and large, and react aggressively when they hear the word "Keto." They've all heard about the diet - it's this year's buzz word, I'm afraid - but in a medical setting they immediately leap from "ketosis" to "ketoacidosis." Kinda like you say "house warming - you're invited" and they hear "house fire." I found this amusing right up until the nurse did this while reading my blood sugar levels on exit from a colonoscopy. She was worried that it read <4 mM, maybe even 2 - I was still somewhat sedated so the memory is a bit fuzzy - and I apparently mumbled that this was great, I was on the keto diet, hoped my ketone level was north of 8, and should be in ketosis. She heard ketoacidosis and, without looking at my chart, tore off down the hall. Next thing I know she's slamming a hypo of glucose into me. I'm not technically diagnosed T2D - quite a story to that - but I am exquisitely sensitive to sugar of any kind. I promptly passed out - the injection will do that - which apparently caused a bit of a fuss in the recovery ward (I confess I wasn't paying attention). Messed me up royally too: I was out for 20 minutes and it pushed me right out of ketosis, of course, so was a mess for the next day or two.
So, about the question of whether the diet can benefit a full-blown type one diabetic: can anyone comment? Idyll knowledge, but I'd love to know more. I'll watch this space. And thank you all: I've found this forum a great resource. The obvious interest and care you display for each other is inspiring. I hope this helped someone.