In the US I do not think there are any OTC drugs which would be fun and safe. Crap like Dramamine is not safe to do, so don't. DXM is a possibility if you're desperate but not really that fun (IMO) and could possibly cause a false Ketamine positive in a drugs test (extremely rare, but within the realms of possibility).
In other countries OTC drugs like Nurofen Plus are available, but codeine is not OTC in the US, plus it can cause a positive test for morphine (since it turns into morphine in the liver).
If you're on probation my advice would be to stay clean, do your time and then you're free to do as you please.