Thanks for the question, and sorry to hear about your tough day at work.
Most people are hired "at will" - this means that you may quit at any time or be asked to leave at any time, for any or no reason. Unless you signed an employment contract stating in clear terms that you cannot be fired except for certain causes, your employer DOES have the right to fire you for something as seemingly unfair as you smelling like alcohol.
If you are fired, you might want to contact your union, if you are a member of one.
My advice (if you want to aviod getting fired):
1. Make an appointment to speak with your manager during a low stress point during the day. Explain that you had gone out the night before and had one drink, but that you usually don't drink and certainly never drink on the job. Apologize for any confusion, and thank him/her for letting you know that you smelled of alcohol.
2. Alcohol will stay in the blood stream for several hours, and others who are sensitive to the smell can still smell it emitting from a person's pores or sweat glands up to 12 hours after the last drink has been consumed. I'm not advocating you never drink the night before work, but in the future maybe wear some perfume/cologne the next day.
Good luck!
If you found the advice helpful, please hit ACCEPT. If you are not satisfied PLEASE let me know, or ask additional questions! Thank You! 
3 Other Experts Agree with this!