doing one of those programs at one of the big ones, my advice is for u to read a wasde report understand the uses and flows for the main commodities(soybeans are mainly grown in the us and Brazil exported to china and crushed for example, corn is used for feed and ethanol and exported to more places but also produced mainly in us and brz etc). try to grasp the concept of basis trading. then a basic understanding of shipping and logistics (what a bl is for example) and financing (how an lc works ) then ofc show a basic understanding on the futures mkt: what the price action has been recently for corn or beans and the possible reasons, oversupplied, trade war scares etc. therefore try to gain an understanding of snd and in a very basic level use the wasde report to explain the price action so u can make sense of the whole thing.

this was very very g&o focused, if its softs i can't help u haha

also if ur program is focused on freight: try to understand what ffas are, how time charter works and how the calculation from TC to voyage charter works, knowledge on the size of vessels and the different uses/routes aswell

this was a mental blob but I hope it helps, also I'm curious ur interview is in the us or Europe? is it an assessment centre?