You never know when you're going to be somewhere and need this. I've found myself reaching for this when going somewhere overnight and a fever spikes out of nowhere.
Infant Tylenol
Always, always keep an extra onesie or set of clothes in the diaper bag! Babies are messy and you don't want to have a blowout or baby spit up and not have an extra change of clothes on you.
Baby Clothes
Feeding
I always make sure to have extra bibs in my diaper bag for eating out or feeding on the go.
Bibs & Burp Cloths
Avent Bottles have been my favorite for all 4 kids. I always make sure to have an extra bottle or 2 in the diaper bag.
Avent : Baby Bottles
If you've got a formula fed baby, having a small can of formula in the bag already is so helpful so that you never accidentally leave it at home and find yourself needing it. I personally loved the Bobbie brand!