Used to do that when I wake up early in the past. In uni, when I have a long day ahead.. and during work. Not so often though because I was lazy :P... Sometimes I just bring [empty] rice bento to work (and buy the side dishes later).

Anyway, the bento thing can still work, I think. Make something in the morning and eat later for lunch. 

On second thought, it's actually troublesome. Hmmm. I never liked washing food containers *so troublesome*.