What should be done if you order a pizza with barely any sauce, barely any bread, and barely any cheese?

You mean, if you get it like that?  Personally I like my pizza with less sauce.  If there's barely any cheese, that's on you, because you should ALWAYS order a pizza with extra cheese, it's the only way to make sure they will put enough.  If it's really horrible, just call them up and tell them you're not happy, they will usually make you a new one and send it out for free.

very small pizza

BARELY ANYTHING  should be  DONE

 one seems to  PROMOTE BARELY  per dictionary in a simply and sparingly way

Eat it,you ordered it.

If I ordered it that way and that is what the pizza maker made, then I would be really happy and leave them a big tip in addition to the price of the pizza.

If that's how you ordered it, that's what you should expect to get.

You get it at a cheaper price.

Tell the manager about it.

they should just make the pizza the way you want it