On SIDES, there are two ways in which all nutritional information is maintained. You can either either add all the nutritional data to items or to recipes. You can change your preference in the navigation under Admin: Global settings > Global store settings > Other settings > Master data settings for items, goods management and accounting. The toggle under "Assign nutritional values to item" will be the setting to determine where the source of your information will be.

For nutritional values added directly to items (meaning the toggle "Assign nutritional values to item" is on), you will have to add the nutritional values directly to ingredients (items marked as ingredients). Nutrition data, allergens, additives, can be added and edited under the section "Nutrition". Ingredients marked as sales items and will be directly synced to Uber Eats with all their details attached. Otherwise, this items can be used to make a recipe in the navigation under Admin: Item management > Recipes and then the recipe can be added to a sales item. The system will take all the allergens and additives and will calculate the nutritional based on the recipes made.
If nutritional values are added directly to recipes (meaning the toggle "Assign nutritional values to item" is off), you no longer can add any information to items directly, even if they are marked as ingredients. You will have to create recipes (under Admin: Item management > Recipes) and attach them to the sales items. You can add nutritional information, allergens and additives to each recipe. Then you will add the recipe to the sales items. You will not be able to add recipes to ingredients, but instead you will have to create a sales item with a recipe for that ingredient.
In the navigation under Admin: Item management > Recipes you can create as many recipes as you want. The nutrition, allergens and additives added here will be passed over to the item it is assigned to.