A second hand Vango Sprint hydration backpack and the best 2l bladder I could find. Last year I had 2 attempts at a 25 mile mtb ride, which I only managed to complete on the third go. All 3 times I had cramping during as well as after the ride. The route itself inspired me to go from 26" wheels to 29" and to lower my gearing down from 17 gear inches to 15. Shortly after getting the bike built I got a neck strain, so haven't had the chance to try the ride again but it's been on my mind. The plan was to try it during the summer but I may give it a bash this year, hence the water bladder