Only you them if you have to.
I understand the reason for weightgain drinks but not protein bars. If you can eat protein bars you can eat a meal. Plus they are very expensive.
I would pick up a can of tuna instead of a meal replacement bar. The meal replacement bars are usually loaded with stuff you don't want, especially the carbs.
It's not going to kill you to eat them, but don't make a habbit out of them.