Sugar alcohols are often found in foods, especially fruit and berries. Some of these include sorbitol, mannitol, xylitol, isomalt, hydrogenated starch hydrolysates, and erythritol. These sugars are not absorbed in the body, so they move with much less influence on the blood sugar or calorie content than the actual sugar.
In particular, two sugar alcohols, erythritol and xylitol, are commonly used in keto-friendly foods. They contain a few carbohydrates and calories, but it's not so much that you find it hard to stay in the ketosis. (They can track the exact carbohydrate number, but it's not particularly important since the amount is so low.) If it's really important to you, you know that stevia and monk fruit are carbohydrate and calorie free.
You are welcome to add drinks such as coffee, smoothies, or shakes to sugar alcohols, or to use them in baked goods or other recipes that require some sugar.
Important Note: Sugar alcohols can sometimes cause gastrointestinal discomfort. They are digested "incompletely", so they are actually digested by the bacteria in your lower intestine, which can lead to rough stomach and gas for some people. If you notice gas, flatulence or diarrhea after eating, swap it for another keto sweetener.