Most interpreters agree that they spake this seriously, that is, that they were willing enough to have such bread (if any such were to be had); but yet not conceiving aright the nature and excellency of the bread our Saviour mentioned; and this occasioned his clear explication of it in the following verse.
Related Commentaries of John 6:34
John 6:34
34 Then said they unto him, Lord, evermore give us this bread.