If you find a 0% APR deal on offer, it means there are no admin fees or interest applicable.
In most other cases, the admin fees and interest are added together to calculate the APR over the total length of the loan. These interest charges are added to the amount borrowed to calculate the total cost of finance.
However, additional benefits such as deposit contributions from the manufacturer or retailer will reduce the amount you need to finance. So even with a higher APR, your total cost of borrowing could still be lower, with smaller monthly payments.