We’re looking for mugs which fit neatly into cars’ cup-holders, so tried them all in both a BMW and a Nissan. Some materials retain heat better than others, so all the cups were also filled with boiling water and the temperature measured with a probe after 15 minutes to see how hot it was. So which is the best for your coffee fix in the car? We filled eight to find out. How we tested them CLAIM:Go to www.BMWAftersalesRewards.com, enter code BA23-10, complete the online Claim Form, and provide your BMW Dealer invoice or ShopBMWUSA.com invoice. Swapping from a disposable cup to a reusable mug isn’t just better for the environment, it can also save you money. Most of the high-street coffee shops now offer a discount for using your own cup,or you can make a drink at home and rely on a decent insulated mug to keep it hot for an entire journey.