Key Tesla customer PepsiCo made initial payments for 100 Tesla Semis in 2017, intending to use the electric-truck fleet to haul its Cheetos, Lays potato chips and Pepsi soda pop to retailers. But according to the food-and-drinks maker and one of its executives with knowledge of the deal, PepsiCo was using only 36 of Teslas promised 100 electric trucks as of this month. The shortfall, which hasn't been previously disclosed, lays bare the challenges for Tesla as it seeks to become a high-volume player in the truck-manufacturing business.