Promotional Dopper Steel Insulated (350ml) Meet the Dopper Insulated collection. The sustainable, reusable (and seriously good-looking) bottles that keep your drink hot for 9 hours, cold for 24. And keep you saving our oceans, all year round. Because the single-use plastic water bottles polluting our oceans don’t care if it’s boiling hot or freezing cold outside. The three-part design means it’s easy to fill and easy to clean - by hand or in the dishwasher (max 65 degrees).