Sprinting endurance is a bit of an oxymoron, but I presume that you mean improving your ability to continue to do repeated sprints.
There are a bunch of workouts I could suggest, but the simplest and best would be something like this: warm up with a 5 min run, then do intervals of 1min hard, 2 min easy, then cool down. Start with 4-6 intervals, work up to 10-12.
When you go hard, make it a challenging pace (roughly the pace you would go if racing a mike) and THIS IS CRUCIAL: don't shuffle the easy parts-go as fast as you can and still recover (it should be a cruise, not a jog shuffle).
Hope this helps