How do you wash your milk bottles outside if you're going to be out from morning to night?

I would pack dish washing liquid is small travel bottles from daiso and bottle sponge in ziplock bags. If you need to santize the bottles, you can get the Medela sanitizing bag however, you would need a microwave. Some baby rooms in shopping malls may have a microwave. https://www.medelabreastfeedingus.com/products/850/quick-clean-micro-steam-bags Alternatively, pack extra bottles? If you are breastfeeding, consider direct latching for zero washing up!