In the warm weather and after workouts maintaining dreadlocks can be tricky. The heat and humidity can cause hair to have an odor. You can use a deep cleaning shampoo made just for dreadlocks to remove all traces of perspiration and product with proper dreadlock shampooing techniques.
A good one is Dred Head Shampoo, this shampoo is great for all types of hair even straight hair with dreadlock. There are many more to chose from. The best thing to do is try several until you have the one you like the best.