Draft emails in Gmail from a Google spreadsheet and a Google doc template: https://katydecorah.com/code/google-sheets-to-gmail-template/

email-drafter.js

// What is the Google Document ID for your email template?
var googleDocId = "abcd0000abcd0000abcd0000abcd0000";
// Which column has the email address? Enter the column row header exactly.
var emailField = 'Email';
// What is the subject line?
var emailSubject = 'You\'re bringing {Type}!';
// Which column is the indicator for email drafted? Enter the column row header exactly.
var emailStatus = 'Date drafted';

/* ----------------------------------- */
// Be careful editing beyond this line //
/* ----------------------------------- */

var sheet = SpreadsheetApp.getActiveSheet(); // Use data from the active sheet

function draftMyEmails() {
  var emailTemplate = DocumentApp.openById(googleDocId).getText(); // Get your email template from Google Docs
  var data = getCols(2, sheet.getLastRow() - 1);
  var myVars = getCols(1, 1)[0];
  var draftedRow = myVars.indexOf(emailStatus) + 1;

  
  // Work through each data row in the spreadsheet
  data.forEach(function(row, index){
    // Build a configuration for each row
    var config = createConfig(myVars, row);    
    
    
    // Prevent from drafing duplicates and from drafting emails without a recipient
    if (config[emailStatus] === '' && config[emailField]) {  
      // Replace template variables with the receipient's data
      var emailBody = replaceTemplateVars(emailTemplate, config);
      // Replace template variables in subject line
      var emailSubjectUpdated = replaceTemplateVars(emailSubject, config); 
      
      // Create the email draft
      GmailApp.createDraft(
        config[emailField],   // Recipient
        emailSubjectUpdated,  // Subject
        emailBody             // Body
      );
      
      sheet.getRange(2 + index, draftedRow).setValue(new Date()); // Update the last column
      SpreadsheetApp.flush(); // Make sure the last cell is updated right away
    }
  });
}

function replaceTemplateVars(string, config) {
  return string.replace(/{[^{}]+}/g, function(key){
    return config[key.replace(/[{}]+/g, "")] || "";
  });
}

function createConfig(myVars, row) {
  return myVars.reduce(function(obj, myVar, index) {
    obj[myVar] = row[index];
    return obj;
  }, {});
}

function getCols(startRow, numRows) {
  var lastColumn = sheet.getLastColumn();      // Last column
  var dataRange = sheet.getRange(startRow, 1, numRows, lastColumn) // Fetch the data range of the active sheet
  return dataRange.getValues();            // Fetch values for each row in the range
}