Is there any feature where an entities pay the fees on behalf of the app user? So that we don't have to fund every customer who use our app?
The account that is the source account of the transaction envelope pays the fees, so that would be one way.
Check fee-bump transactions, a new feature available since the protocol v13. Fee bumps supported by all major SDKs.
Pros:
Cons:
2 x base_fee
1 x base_fee