I have been in about 6 sprint triathlons. The key thing about sprint triathlons is that they only take about 80-90 minutes to complete for the average person. With such short distances, you really don't need to get carried away with a full training program unless you are completely out of shape or if you are planning to win the event. I have entered a couple event without really training at all. If you want to do your best, some weight training will be beneficial -- I like to do a cross-training routine where I can go through key exercises in short time. But nothing beats running, biking, and getting in the pool. For swimming, focus more on upper body movements to conserve your legs for the bike and run. Space out different exercises throughout the week, even pair them up as the event nears. There are many training schedules to be found online. And of course, practice your transitions -- get the steps memorized, be organized, and minimize unnecessary steps like fueling up if you can do that on your bike. Most of all have fun -- a sprint triathlon is just the beginning!