Update

//  Create a Map to store all the data of a Vendor
Map<String, Object> vendorMap = new Map<String, Object>(); 
    vendorMap.put('DisplayName','Lap Care Match');
	vendorMap.put('Id','101');
	vendorMap.put('SyncToken','0');
        
//  Initializing the RequestJSON Data to be passed.
Map<String, Object> requestJSONMap = new Map<String, Object>();
    requestJSONMap.put('vendors', new List<Object>{vendorMap});
    String reqJSON = JSON.serialize(requestJSONMap);

Map<String, Object> reqObj = new Map<String, Object>();
    reqObj.put('version', '1.0');
    reqObj.put('action', 'updateVendor');
    reqObj.put('requestJSON', reqJSON);
    //Required, if QuickBooks Multi-Org is enabled in Breadwinner. 
    reqObj.put('qbOrgId', '!aa00TM');

//  Placing a request to Breadwinner Global API
Map<String, Object> respMap = breadwinner_qbo.BreadwinnerQBAPI.call(reqObj);
System.debug(respMap);