Remember: you cannot add modifiers manually in SANITY - you can only update existing ones or delete a modifier that the marketing team shouldn’t have associated with a specific menu item in MDS.
In case you have added it manually in SANITY, please delete them and make sure your Marketing team has configured the modifiers in MDS. They are synched with staging every day at 6.30am, so you should see them in staging within 24 hours (you can also restore the previous version of that item from before you deleted the MDS modifiers). For more information, please read question 4 of this section.