I've said this before, and I'm sure I'll say it again, but no one seems to take the advice...
Click on a building and take note of where that donut button is. Notice how its in the exact same place on the screen every time, for every building? It's in the middle of the right side of the screen. Avoid clicking in that spot. If you follow this rule while you're tapping ferociously, it won't matter what you accidentally click on. I collect all of the individual $ and xp (I like the sound) and I do it fast and carelessly. I just keep repositioning the screen so that the building, money, and xp are all on the left side of the screen, far enough away from the donut button. I haven't wasted any donuts since I started doing this!