denis_alekss,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<ul id="list1">
<li>Кофе</li>
<li>Чай</li>
<li>Кола</li>
<li>Виски</li>
<li>Коньяк</li>
</ul>
<script>
let elem = document.querySelectorAll('#list1 > li');
let f = document.createElement('li');
f.textContent = 'Водка';
elem[2].parentNode.replaceChild(f , elem[2])
</script>
</body>
</html>