I take it that you make your OWN sushi? Most ALL commercial sushi contains sugar, and plenty of it. It is either in teh rice wine vinegar or they add Sugar (that really fine white form) when they mix the vinegar into the cooked rice as it is cooling. Be sure to always make your OWN sushi, I don't trust these places where you buy sushi to make it just for you. Sushi tastes good often because it is sweet.
The best form of sushi is quinoa sushi, yum! It is made from quinoa, and tahini (sesame seed paste) is used to keep the quinoa together. You will find a recipe online for sure. Once you try this, you will never go back to commercial sushi.