Almost every single other sugar substitute is filled with erythritol as an additive. Monk Fruit products tend to be really bad offenders. Check the labels carefully.
I casually follow the FODMAP diet and avoid sugar alcohols where possible. It's surprising how many sugar substitutes include it, sometimes as the primary ingredient. I've found a pure stevia powder that tastes okay, but it isn't cheap and is only sold in a local health food store.
This I found out the unfortunate way. I used some popular monk fruit sweetener... packets were just monk fruit but the bulk packages were monk fruit/erythritol blend and I didn't pay enough attention to the label. Made lemonade with it.
Aspartame is fine in things like soda, but the reason erythritol is mixed with monk fruit (and perhaps aspartame as well?) is it is closer to the sweetness level of sugar in terms of sweetness per gram, and so it's usually easier to use in recipes that are based on sugar quantities.
