Google Sheet script that will convert cells A2:D1000 into a downloadable XML file.

categories.js

function doGet() {
  // The sheet that contains the category information.
  var categoryDataSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Categories");
  // The first row of the sheet that contains the categories' name, description, parent, banner image, and list image.
  var categoryAttributes = categoryDataSheet.getRange("A1:D1").getValues();
  // Range of rows and columns that contain the category information.
  var categoryData = categoryDataSheet.getRange("A2:D1000").getValues();
  // XML document object.
  var document = XmlService.createDocument();
  // Root element of the XML output.
  var root = XmlService.createElement('manufacturers');
  // variable that holds the generated XML document.
  var xmlOutput;
  
  for(var i = 0; i < categoryData.length; i++) {
    
    if(!isEnd(categoryData[i])) {
      
      // Begin category tag.
      var category = XmlService.createElement('category');
      
      for(var j = 0; j < categoryData[i].length; j++) {
        
        var tag = categoryAttributes[0][j];
        var text = categoryData[i][j];
        var categoryAttribute = XmlService.createElement(tag);
        
        if(tag == "description") {
          
          categoryAttribute.addContent(XmlService.createCdata(text))
          
        } else {
          
          categoryAttribute.setText(text);
          
        }
        
        category.addContent(categoryAttribute);
        
      }
      
      root.addContent(category);
      
    } else {
      
      break;
      
    }
    
  }
  
  // Put everything together and output it.
  document.addContent(root);
  xmlOutput = XmlService.getPrettyFormat().format(document);
  Logger.log(xmlOutput);
  return ContentService.createTextOutput(xmlOutput).downloadAsFile("categories.xml");
  
}

function isEnd(row) {
  
  for(var i = 0; i < row.length; i++) {
    
    if(row[i] != "") {
      
      return false;
      
    }
    
  }
  
  return true;
}