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

I just rinse w the hot water / shake / swirl the bottle w hot water - at the dispenser in the infant room, u may kana ur fingers pain tho. Then I put in ziplock and put inside my cooler bag - which contains my pack of milk n ice packs. Save space and use milk bag, then this method can last u 2-4 pumps. I do it v occasionally but baby is alright. If ur cooler bag is big enough/ ur bag is big enough, u can bring another set of pumps etc