Lemmon Water? Same Category as Black Coffee

I'm new to this and just finishing day 3 of 18/6. I've been super strict with just water and coffee. However, I'm a huge fan of squeezing half a lemon over ice and adding water to a 40oz cup in the evening, as coffee would affect my sleep. I know there are no truly zero-calorie drinks, even when considering coffee. I'm just curious if fresh lemon juice would fall into the same category as coffee for intermittent fasting?