Cash makes the world go round. Paper currency is accepted by everyone and doesn’t need any technology to work. Keep your denominations under $20; sometimes it’s hard to ask for change. Be realistic and keep a few hundred dollars.
You can run out of cash and still have money. Don’t forget how amazing your phone’s digital wallet can be. If there’s electricity you may be able to make purchases without cash or a wallet. Consider Apple Wallet, Google Pay, your bank app, or brand specific apps for coffee shops, grocery stores, or fast food restaurants.
Once I was driving to Starbucks to get some coffee beans. After picking up my beans, I hoped in the car and headed back home. On the way I passed a police car which suddenly made me realize I had left my wallet at home. I had so completely changed my behavior to pay with my Starbucks app that I forgotten the habit of driving with my wallet and ID. Something I had been doing for over 30 years.