Nothing you do or say is ever for no reason.
When I pick up the phone to call my husband at his office in the middle of the day, I might say it's for no reason, but it's really because I was lonely or bored and I wanted to have a grown-up to talk to after chatting with my 4-year-old about worms all morning.
When I open the fridge and stare aimlessly into it, I might say it's because I don't know what to eat, but it's really because I know what I want (CAKE!) and I know that it isn't what I should be having (SALAD!).
When I lie down on the sofa and flick on the TV, I might say it's because I had nothing else to do, but it's really because I either a) have something to do that I'm avoiding; or b) need some down time.
There is always a reason; there is always an objective. Company; food; relaxation.
It should be the same for your characters. Let every word and every movement be guided by that character's objective in that moment.
What are some of the objectives in your characters' hearts? What is the weirdest objective any of your characters has ever had?