Hi, I've only had a look at the initial link (APEX TX5). If you ask me, the ingredients listed could broadly be described as stimulants which would be present (to in some amount) in the food/drinks generally consumed by the majority of people on a daily basis:
Caffeine
Theobromine (in chocolate, especially dark chocolate)
Carnitine (meat)
Phenylethlyamine (lots of things, but chocolate again)
Tyrosine (red-bull, meat, nuts, milk etc.)
Anyway, the amounts of each per-tablet don't seem to be listed but if they're pharmacologically significant then you would certainly get an energy boost (if only from the caffeine). The impact of the other amino acids would depend on your diet, but are unlikely to have as immediate an impact as the caffeine. Side effects from any of the above are highly unlikely (unless you took alot of them at the same time).
I'm not a fitness guru, but I'd suspect that they would be most effective if taken before a workout (to give you the most energy for exercising), although they might also work as a post-exercise supplement (prevent an energy lull? maintain metabolism for longer?).
Phentermine.... That one sounds like it's quite hard on your body. No wonder they limit its use.