Many milk substitutes have a natural sweet taste. Try adding almond milk to your coffee. I personally drink mine with oat milk and don't add sugar.

I am also skeptical of the impact of sugar on acne. I can find no reputable results about the subject by Googling. All I find are articles from disreputable sources such as Huffington Post, Daily Mail and Marie Claire and they aren't scientific journals...they're mostly online newspapers and beauty magazines trying to sell fads to people. I can find 0 actual studies on the subject.