Hey there! I often have clients track food in a couple of different apps for SPECIFIC purposes. Cronometer is my go-to app for tracking macronutrients, micronutrients, and most importantly, SUGARS. A lot of my clients use Cronometer to track their own sugars and keep track of their average daily sugar intake.
If you are using it as well and having trouble adding a custom food, this might be the EXACT tutorial you need!
I hope this helps!