Is Sugar Keto?
Sugar is not keto-friendly because it is a high-carb sweetener that may kick you out of ketosis even with small amounts.
Sugar is a high-glycemic sweetener so it will prevent your from reaching or maintaining ketosis even in small amounts.
It is also linked to an increased risk of chronic diseases such as obesity, cardiovascular disease, and diabetes.
Too Much Carbs!
Sugar should be avoided on keto because it is very high in net carbs (100g of net carbs per 100g serving).
It is important to limit your net carb consumption to 20g - 30g per day to stay in ketosis. You can calculate your ideal daily net carb allowance by using this keto macros calculator.
As an alternative, you may look for other sweeteners that are low in net carbs.