It really bothers me when the waiters and barista are screaming that they are starving, among other things. I wonder if there is a way (with MasterController or whatnot) to click on any sim and max out his/her motives? Like "Make all happy" on mailbox function in residential lot. I looked around but couldn't find a function like that.

I think you can with MC, under direct (not sure what its called in english) you can click max motives on the chosen sim.

Thanks, found it. Under "Intermediate" in English menu.

With awesomemod you just type makehappy in the console.

When waiters, barista bartenders or other role Sims complain about low needs it actually means that the link between the role object (bar, food synthesizer, register) and the Sim is broken. When everything works correctly their needs are fully maxed out and locked, so they should really be in a constant state of elatedness.
One thing that can cause this link to break is when for some reason or other the Sim or the role object were reset. Another cause is if you use any version of NRaas Register that is not the most recent test version (78a) by Chain_Reaction. The last test version still does it occasionally but it has become much better.
If you are using Register you can fix this until the next time it breaks again by doing this:
(1)Click on the role object and remove the Sim assigned to it from the role with Register
(2)a. Either click on the role object and use DebugEnabler to reset the object (NRaas/DebugEnabler/Object.../Reset)
(2)b. Or go into Buy mode and replace the object.
(3)Click on the role object and reassign the Sim with Register

Here's more information if you need some:
http://nraas.wikispaces.com/share/view/66063258
http://nraas.wikispaces.com/share/view/66896774