Select products to recommend and add these on your Training Plans, Workout Templates Custom Workout Videos within Trainerize. Any accessories that your client will need, common ones are gym mat, health ball etc. Add a required accessories detail in your video, exercise template or training plan with a link to Buy from Amazon using the generated link out of your Amazon Associate account. This is excellent passive income as the link may be there for all your clients within exercise videos.
You can recommend real equipment for the buyer of their training plan, again with an affiliate link. A non-public advice from their trainer has terrific sway as you are the professional, you recognize good kit from bad kit, they will recognize your advice and your probabilities of a follow up sale are good.