The best preparation doesn't involve studying detailed test examples or cramming about the fundamentals you have become a bit rusty on since your University CS days.
The ultimate prep for a tech interview or any interview for that matter is plenty of rest, reasonable research on the company you are interviewing with and getting a clear understanding of their expectations for the role you are applying for.
Tech interviews aren't designed to test how much study and preparatory work you can do, the most effective Tech interviews are designed to find out what your general competency is with specific technologies and what sort of coder personality you align to. The tests aren't designed to find out how good you are in one specific circumstance, they want to gauge what calibre of code you will produce should you work for them on a daily basis.
My advice: Get plenty of rest, stay calm, do your best on the day and if you failed miserably then chances are you avoided joining a company where the level of expectation would have led to unnecessary stress and pressure down the line.