The numbers were reported in the campaign's monthly filing at the Federal Election Commission.
The drop followed a sharp fall-off in fundraising. Although Sanders has led Hillary Clinton in fundraising every month this year, April receipts totaled only $26.9 million, versus $46 million in March.
Sanders has poured money onto California's costly TV markets, as he fights for an edge in the June 7 primary. His March fundraising — his strongest this year — barely outpaced his spending. And in April, spending exceeded receipts by 43 percent.
Clinton's FEC report shows April fundraising off 7 percent from March — $25 million versus 26.8 million. But she spent relatively little, $23.9 million, and finished April with $30.2 million available. Her cash on hand has been in the range of $30 million on six of the seven reports filed since the campaign began.