cryptoupdates.gs

function getUpdates() {
  updateCell("B3", "ripple")
  updateCell("C3", "bitcoin")
  updateCell("D3", "ethereum")
  updateCell("E4", "litecoin")
  updateCell("F4", "iota")
}

function updateCell(cell, code) {
  const response = UrlFetchApp.fetch("https://api.coinmarketcap.com/v1/ticker/" + code + "/?convert=EUR")
  const data = JSON.parse(response)[0]
  const sheet = SpreadsheetApp.getActive().getActiveSheet()
  const range = sheet.getRange(cell)
  const [ p1, p2 ] = cell.split('')
  const percRange = sheet.getRange(p1 + ++p2)
  percRange.setValue(data.percent_change_24h + '%')
  percRange.setBackground(data.percent_change_24h > 0 ? "#c8e6c9" : "#ffcdd2")
  range.setValue((+data.price_eur).toFixed(2))
}

My take on this. Simplified and removed hardcoded column letters, specifying the range instead

function getUpdates() {
  const sheet = SpreadsheetApp.getActive().getActiveSheet();
  
  // Update the range based on the total number of cryptocurrencies you have in the spreadsheet
  const range = sheet.getRange('B1:H1');
  const cells = [].concat.apply([], Array(range.getNumColumns())).map(function (x, i) {
    return String.fromCharCode(66 + i);
  });
  
  cells.forEach(updateCell);
}

function updateCell(column) {
  const sheet = SpreadsheetApp.getActive().getActiveSheet();
  const codeRange = sheet.getRange(column + '1');

  const response = UrlFetchApp.fetch('https://api.coinmarketcap.com/v1/ticker/' + codeRange.getValue() + '/?convert=EUR');
  const data = JSON.parse(response)[0];

  const priceRange = sheet.getRange(column + '3');
  
  priceRange.setValue((+data.price_eur).toFixed(2));

  const percChangeRange = sheet.getRange(column + '4');
  const priceChangeRange = sheet.getRange(column + '5');
  const bgColour = data.percent_change_24h > 0 ? '#c8e6c9' : '#ffcdd2';
  
  percChangeRange.setValue(data.percent_change_24h + '%');
  percChangeRange.setBackground(bgColour);
  priceChangeRange.setBackground(bgColour);
}