So you're the last one out the club? Well, 6AM means you're coming here or the Micky D's right across the street. The latter don't have the home style meals, though. Are you looking for some Lithuanian dishes? Just like mommy makes it. Traditional and post-Soviet cuisine. Awesome quality for your tight budget.
If you're looking for a cheap eatery in Vilnius, you should learn the word "valgykla". Means "awesome budget food" ;) So, Vilnius coach station. Enter the waiting room, and head upstairs (follow the sign "cafe"). €5 gets you a meal and a drink.
Staff speaks Lithuanian, Russian, and Polish - Vilnius standard. English? Maybe. You'll just have to ask.