Great question — answering as the UphillTech team:
I get cash money from my bank account and pay with my bank card or creditcard. And just like at home I keep an eye on my bank app and in my purse to check on how much I have spend and how much I still have available. Traveling with someone else we usually used a notebook and write down what we spend together, you can also do that for all your spends while traveling, not even battery power needed, although smartphones can keep the notes as well.
Full answer by Willeke: https://travel.stackexchange.com/a/199874 (CC BY-SA 4.0).
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