Blood sugar is not affected by only "sugar" (sucrose). All carbohydrates are converted into sugars by your body, thus potatoes, grains (rice, bread, pasta, etc), fruit (and juice) also cause your blood sugar to spike.

It's not only people who drink lots of soda and eat candy, sweets, and desserts...it's also people who have a carb-heavy diet with lots of bread, pasta, tortillas, chips, etc.

The advantage of those foods over sugar is they usually come with fiber, which buffers their absorption and reduces the blood sugar spikes & insulin response.

I can eat a bagel with cream cheese and see a massive blood sugar spike in my CGM, it's definitely something to be avoided or moderated.