Was this to harsh on them?

Yeah.. I think that you over-punished her. And my question is why is a 3yr.old little girl doing drinking POP(soda) on a regular basis as to get it taken away as a punishment. Anyways.. The rule of thumb is to have a level of punishment system. Plus you sat her on a time out for longer than her age which is a HUGE NO NO!!! It's one minute per age. I don't believe you have resolved this situation correctly and that's why your feeling remorse for it now. You should have taken time to calm down before punishing her. Remember that a child will go as far as you allow them... You loose your patience and they ultimately get what they was looking for which is attention rather it's positive or negative.