I'm into keto. You should give xylitol a try, as it's bulk and texture match table sugar closely and can be used interchangeably. It can cause gastric issues for some in certain quantities.

Debates on /r/keto rage all the time on whether artificial sweeteners cause an insulin response. And if it does, whether or not it is a chemical or psychological response.

The science on the topic seems to be nacent at this point, at least from this layman's view.

The most common recommendation is to simply give up sweets entirely, not just carbs. As one hooked on the Monster Zero line of power drinks, I have a tough time with this myself.

Aspartame is much, much sweeter than sugar (it actually has the same calories/unit mass as sugar) and sugar does more than provide sweetness in recipes (especially chewier things like cookies). Aspartame also degrades at baking temperatures. So it just isn't a good substitute.

Maybe try sucralose, which you can just swap in for the same amount of sugar (Splenda is a famous brand).

Splenda does have a version of the product specifically for cooking - it seems to have a lot of 'filler' to get it to the similar consistency and volume of regular sugar (1 cup of sugar being as sweet as 1 cup of the cooking Splenda). That being said, it's best to just avoid the stuff when you can. I've found eating things with tons of Splenda in it can be pretty gross - I experimented with it a bit years ago when I first started going low carb and had bad sugar cravings, but wouldn't touch that stuff nowadays.

Yes, I just eat things with normal sugar if I want something sweet.

But apparently the commenter I replied to had not considered the potential differences between the substitutes, so I pointed out a way forward.

I was confused about sucralose though, I hadn't realized that it required fillers to use as a 1:1 substitute. The fillers also apparently are not very hydroscopic (which is a major role that sugar plays in baking, in addition to being sweet).