Voters should have the option to remain in the EU if they are unhappy with the result of Brexit talks, she said.
The party is also discussing electoral pacts with fellow parties in a "number" of constituencies, she added.
Ms Lucas is the Greens' only MP and the Liberal Democrats have agreed not to contest her Brighton Pavilion seat.
She wants to maximise the number of MPs who will support moves for electoral reform and try to win or defend seats against the Conservative Party.
"Discussions are going on in a number of constituencies. Whether that will deliver any results, I can't tell you - watch this space," she said at an election event in Hackney, London.
The Lib Dems have previously said a "limited number" of local parties are considering similar deals ahead of the June 8 election.
Bristol West and the Isle of Wight are among the Green Party's target seats, as it pushes for a second MP.
Outlining the party's policy on Brexit, Ms Lucas said leaks and reports during the weekend about Brexit talks between Prime Minister Theresa May and European Commission president Jean-Claude Juncker "confirmed our worst fears really - that Theresa May is going into these negotiations utterly unprepared, completely arrogant and not understanding how the EU works".
"In the days following the EU referendum, the Green Party called for the British people to have a further say on the details of any Brexit deal and we stand by that position," she said.
The Green Party accepted that the 2016 referendum result was an instruction to the government to begin Brexit talks, she said.
But it should be the "start, not the end" of the process, with people having a say on the final deal - including an option to remain within the European Union, she said.
The Lib Dems have also promised a second referendum on the Brexit deal.
Theresa May says that the Conservatives would make "a success" of Brexit and has promised to give MPs a vote on any deal that is agreed between the UK and the EU. Jeremy Corbyn says Labour would not hold a referendum on the final deal, but wants MPs to have a decisive say on it.
A second referendum on the details of any Brexit deal should be offered to voters, Green Party of England and Wales MP Caroline Lucas has said.