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

Lol, im a very rugged mom, i feed baby, and immediately rinse them to minimized the residue sticking in the bottle. I realize if its not wased immediately it will be harder to wash. Otherwise i normally go to starbucks or mac whatever i can find, ask for hot water, shake and rinse. Thats just me.