Clear

<div id="spreadsheet"></div>
<script type="text/javascript" charset="utf-8">

    $("#spreadsheet").kendoSpreadsheet();

    var spreadsheet = $("#spreadsheet").data("kendoSpreadsheet");

    var sheet = spreadsheet.activeSheet();

    sheet.range("A1").value(1);
    sheet.range("A2").value(2);
    sheet.range("A1:A2").clear();
</script>