I'm not sure if I understand the question. No bank will give you $300 in return for $30. Banks are in business to make money, not to give it away. If a bank loans you $300, they will want the full $300 back, plus interest.
Apple Cash - Apple
According to Apple's FAQ ("How do I add money to my Apple Cash card?"), you can transfer funds to your Apple Cash account from a debit card in your Apple Wallet. (The balance may also increase if somebody sends money, and if you have an Apple credit card and have told Apple to deposit "cash back" amounts to Apple Cash.)
There is no mention of a loan option. It's an electronic funds transfer system, not a credit line. If you want to add $300 to your Apple Cash balance, you must provide the full $300.