Parenting these boys is the hardest thing I've ever done

What to do when they ABSOLUTELY WON'T do what I've asked them, and I've been patient yet firm, clear and helpful, made sure certain variables were taken care of (such as not asking them to do something on an empty stomach). Then what? I can (and do) get angry. Doesn't work. I can be calm but punitive (taking away rewards, giving fines, etc). Doesn't work. I can encourage with incentives (time together, fun activities, etc.  Doesn't work. NOTHING SEEMS TO WORK. And I'm asking totally reasonable things. Put away backpacks and lunch boxes. Bring your stuff in from the car and work together to take out the garbage and recycling. How long do I hold a grudge? My disappointment and/or anger doesn't seem to make any difference on whether they do it or not, so I'm the one choosing to have a sad and disappointing afternoon. Yet if I'm not expressing my disappointment, then how will they understand that they shouldn't act this way. They'll just think it's ok. And then I'm just breeding a bunch of defiant, unhelpful, disobedient future teenagers. What do I do?