As such there is no clear answer which product is good to promote your business? There are various factors which can decide best one for you like need, budget , size and the event.
You might have to consider the imprint area . On larger imprint area, the print area will be big. Water bottle , drawstring bags, tote bags, umbrella have large area.
Also might have to see, if those are durable or not.
If you need suggestion, you can always contact allpromoitems.