As far as creatine goes I think the main benefit is from training with the increased water content that the body takes on when on creatine during training. We tried this with a world cup ski team some years back with varied results. Everyone looked a little fat to be honest.

But if they put on some more weight (via fluid retention) and train at a heavier body weight then they got a bit stronger. When they stopped the creatine and lost the water they felt relatively stronger than previous. taking on the whole body water was interesting as everything perhaps worked harder which might be better that say running with a weighted vest?

Low does caffiene I believe has shown to increase performance in "some" long distance runners. The results showed that diluted caffiene could assist some but not others. Any more comments out there?