Breastfeeding diet

Hello mummies, just wanted to ask if formula is better than breast milk if my diet is not that healthy? Like I order food delivery for most my meals so its really quite difficult to have a very healthy diet and my cravings are usually not very healthy e.g bubble tea, fast food, instant noodles etc. Although i do eat salmon, cod fish, oats and fruits at times but I'm not sure if its enough? I read online and the results vary. Thanks all!!