Getting nasty is not the direction you need to take. This will only hurt you should you offend a customer. it may cost you your job.
I'd like to think and sincerely hope that your management team approach their people and job with the utmost professionalism.
Breaks should be planned and indicate on the shift sheet as per the basic training systems in McDonalds. And from time to time we do get busy and require the help of our staff to satisfy the customer.
However, your working nine hour continuously without a break is an issue. The approach would be to speak to that shift manager one on one about the fact that you need a break. (don't just say i need a break ) explain that "I have worked 9 hours, I am run down and have not yet had a break." Take the courteous approach first. If your manager does not see your need then I too am disappointed in their concern for your welfare.
Legally, Half Hour breaks are un-paid, so should you miss out on yours then you need to be paid for that time. 10's(15's in NZ) are paid breaks, should you miss out on them then you are entitled to have that time added to your wages for that shift.
But most importantly, If you say nothing, you get nothing. We are all human and make over sights and mistakes. Take the responsibility on yourself to stand up and be counted, If your missing out SAY SOMETHING
to someone who can help.
In the meantime, Thank you for you r hard work an continued support for your customer. You are an asset to your team.