Im joining in this discussion as an observer and hope to glean some advice.
Ive just swapped some courgettes for some sweetcorn and I know not the first thing about then other than to plant them in blocks.
Cut the bottoms off and use them as cloches to get them established....
They provide protection from most animals and an extra bit of warmth too!!
When the sweetcorn starts growing out of the bottleneck (make sure lids are taken off!) then can take them off or if still wanting protection cut the top part of the bottle off so u still have a protective ring around the base but plenty of space for the plant to grow..
Hope this helps!
(I have a near-addiction to diet coke so have find plenty of ways to recycle the bottles!!!)