Can we enter text without using sendKeys() in Selenium WebDriver?

Yes. We can enter/send text without using sendKeys() method. We can do it using JavaScriptExecutor.

Using DOM method of, identification of an element, we can go to that particular document and then get the element by its ID (here username) and then send the text by value. Look at the sample code below:

JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript("document.getElementById("username").value=myusername");