[{"_id":1,"favorite":{"color":"red","foods":{"fruits":"banana","fastfood":["burger","sandwich"]}}},{"_id":2,"favorite":{"color":"green","foods":{"noodles":"ramen","fastfood":["fries","burger","corn dog"]}}},{"_id":3,"favorite":{"color":"red","foods":{"soup":"cream soup"}}}]

db.collection.find({$expr:{$eq:[["burger","sandwich"],"$favorite.foods.fastfood"]}})