Called Flexileasity, the product aims to reduce company overheads and administration involved in fleet management, funding and maintenance for fleet managers running between 10 and 50 vehicles with low or average mileage requirements.
A spokesman said: 'When we spoke to fleet managers about their number one priorities, some clear themes emerged.
'We looked at how a rental option may prove to be the perfect solution and created Flexileasity to enable fleets to manage vehicles as needs change. It is often very difficult to predict a company's exact requirements, which can lead to pool cars standing empty.
'By choosing a long-term rental agreement with Sixt, cars can be rented as required from periods of one day to five years but with no penalties or additional fees for returning the vehicle early and no hefty penalties to pay for excess mileage.'
The spokesman added that as the vehicles were rented, the onus was on Sixt, not the fleet, to take on any maintenance and servicing requirements.
Vehicles available range from superminis, saloons and executive cars to vans, minibuses and trucks. Included in the rental price is delivery and collection, road fund licence, repairs due to fair wear and tear, routine servicing and maintenance as recommended by the manufacturer, 24-hour breakdown cover, replacement vehicles for mechanical breakdown and special fittings and livery.