If you go down the cork bark route then I'd make sure you sterilise it first - Jellypigs is right... you often get 'hitch-hikers' with it
I've never used cork bark for my turtles as it has to be wedged in... I'm worried that when it gets wet and expands that it might place stress on the glass. It probably wouldn't but I'm a bit of a chicken when it comes to my tanks.
Turtle Docks (by Zoo-med) are - in my opinion - the easiest and most user-friendly basking area available. There is no rick of damage from heavy rocks, easy to clean, easy to relocate and rises / falls with the water level. The only problem is they
sometimes perish after about a year or so.
I personally wouldn't give my Sliders and fruit... just stick to dandelion, some carrot now and again, duckweed, the odd
defrosted lance fish, dried bugs (such as crickets) etc.
Avoid Mealworms as they are very fatty and contain little nutritional value (although the Mealworm beetle does). If you offer fruit then you might create feeding problems - Sliders can sometimes turn their noses up at what should be their staple diet and hang-out for the 'tasty' treats. Try to avoid feeding live fish, crickets etc. as you may be introducing parasites (especially with crickets)
Sam