Select a piece of furniture that resembles a bar. A long buffet or a high-standing, narrow table will work.
Paint the piece of furniture brown, dark green, red or black. Think of typical bars you like. You will need to place the furniture on a drop cloth, prime it and then paint it the main hue.
Position the table in your basement in front of a blank wall. You need enough space away from the wall so that you can stand behind it. Place barstools on the other side.
Hang bar signs or beer signs on the wall behind the bar.
Hang wooden shelves on the wall behind the bar. Place beer and wine glasses on the shelves.
Set up bottles of alcohol and buckets of ice directly on the bar.
Invite your friends over for a drink.