Just regular "SEPA slow" (i.e. SEPA credit transfer), as far as I know, unless they're financed by a mortgage/loan anyway.
Some banks offer "rush payments" for that use case in particular, which I believe essentially correspond to either an RTGS payment and a phone call or fax to the receiving bank ("hey, can you check your TARGET2 account real quick for our transfer <reference> and credit your account x for the sum please?"), or just a regular old SEPA credit transfer with somebody making sure that it's not caught in some AML or fraud control queue for several days. It's not a pan-European standardized scheme, in any case.
Some banks offer "rush payments" for that use case in particular, which I believe essentially correspond to either an RTGS payment and a phone call or fax to the receiving bank ("hey, can you check your TARGET2 account real quick for our transfer <reference> and credit your account x for the sum please?"), or just a regular old SEPA credit transfer with somebody making sure that it's not caught in some AML or fraud control queue for several days. It's not a pan-European standardized scheme, in any case.