Canada Tax Questions Answered by Experts
Products you show during presentations best fit under "Supplies" (line 8811). However, if such products were to be sold to customers, they would become inventory, which you should already know how to report. Sending products to customers (without payment) would probably be a "business gift", and a plausible advertising expense.
I don't see how a presentation could fall under "Cost of Goods Sold"; your efforts with the demonstrations don't go into a product sold to customers.