How can I hide money in a prepaid debit card?

Reposted from r/ abusiverelationships so I can find financial advice.

My husband refused to join bank accounts ever since we got married. I am a stay-at-home mom and he doesn't let me work. Our kids and I have been living with a relative, but he is still financially abusing me. I am in the process of trying to improve my financial situation.

He rarely gives me money and he often does the grocery shopping. When he gives me a little bit, he screams at me for not saving some of the money. When he does actually give me money, it barely lasts long when feeding 4 kids and 2 still in diapers. It doesn't last a whole week. Given that he screams at me telling me I need to save, you'd think he would be happy when I actually do save. Last winter, I saved $150 that I received as Christmas gifts, and he got SO MAD saying I was lying that I didn't have money and that I was keeping secrets from him. He found this out by looking at my bank app on my phone. (In my opinion, I feel like having money in a savings account is the same as not having money, because savings should be put away for emergencies and not used unless absolutely needed. He thinks savings should be spent.) He regularly brings this up as evidence to why I can't be trusted. He uses this to justify his decision to why I can't share a bank account with him.

How can I save money digitally without detection? I know I can hide cash, but I want to know how I can make digital purchases undetected. He checks receipts, so I need to be stealthy about how to get cash to buy prepaid debit cards. Receipts show when getting cash back. My husband also sometimes looks at my bank account. What is the best prepaid card? Do any not have fees? Given how little money I can hide, a $5 fee might empty my whole card. Also, I want one without fees to refill.

Side note, do you know of any stores that do NOT show cash back in the receipt? I am in the USA.