Registered Dietician Mark Rifkin writes:

For Cole,
According to the Taco Bell website, there is no sugar or sweetener in
the pinto beans. However, there is sugar in the tortilla, and the total
bean burrito is listed as having 3/4 tsp of sugar. Additionally, there
is partially hydrogenated corn oil, providing 0.5 g of trans fat per
burrito. Nutritionally, I'd be more concerned about the trans fat than
the sugar.