If your friend play much with casino or betting. you can easy find many bet site accept with bitcoin.
if you have friends who do exchange much bitcoin or they cashout bitcoin with bitcoin debit card then you can find some website for bitcoin card.
for myself most of my friend doing mining and they cashout bitcoin daily with plastic card and i refer them using uquid card with my link (https://uquid.com/account/register/a?u=UQ141985) . you no need have website or have to put banner. all you need is copy the refer link for your friend register account. all done. you will get 10% commission instant for every transaction your friend make.