For example:
The unreliable employee often engaged in __ activities like smoke breaks, smalltalk with his fellows, and playing Solitaire during work hours.
On Friday afternoons, the employees would often goof off and perform __ activities.
Fred's mind often wandered while performing menial tasks and he thought about __ activities he would rather be doing.
Best candidates so far:
counter-productive/non-productive/unproductive
unprofessional (?)
Bonus: Come up with a word that eliminates the need for the word activity altogether:
The project will not get finished any sooner if you keep wasting time on __.