Hello,
First, not a good idea to take medications prescribed for others. Definitely should be seen by a physician for a proper diagnosis and prescibed your own medications.
Secondly, if you are asked what medications you are taking when applying for a job you should probably be truthful, but now you will run the risk of having to explain taking a drug that has not been prescribed for you. The amoxicillin won't be the big deal but the klonopin may be.
I think it's better to be forthright with a potential employer about all the medications you're taking--even if you don't get the job. I have heard too many stories about people who got themselves into trouble by not being completely honest about this. The reprimands were pretty severe. Many lost jobs because of the deception.
I think it's best to tell them that you took the Klonopin and how much. I don't know if it'll show up on the drug test, but it's possible since it does have a half life and stays in the system longer than other medications. Go ahead and tell them about the antibiotic. I don't think that should have any bearing on your job qualifications, since most people only take the antibiotics temporarily. Definitely be honest about the Klonopin, because it is sedating.
Remember, people caught for buzzed driving rarely ever think that they're actually impaired. Sometimes, the person hasn't even had more than one drink and doesn't believe there is enough alcohol in him to hurt anything. But, I know about a story of someone who had only had one serving of alcohol and wasn't actually drunk, but he made some kind of driving infraction and got pulled over. The breathalizer test said that he was impaired. This could've been more serious. He was so embarrassed. He never had a drink out in a restaurant ever again after that.
A friend of mine discovered that watching her sodium intake actually stopped her RLS. I thought I would mention that, since it might save you from having to take very much of the Klonopin. I have only a few of those on hand myself, but I rarely ever take them, because they affect me pretty strongly and for a long time. Ambien does, too. I mentioned Ambien, because Klonopin is sedating.