A little rubbing alcohol will cut the stink. I've heard that baby wipes will too.

What is your alternative? If they have small individual bathrooms you can just arrive a little early and shut yourself in and give yourself a complete sponge bath. If its a more standard multi-use restroom then it will be a little harder.

Strong shots of cologne won't do. It has to be pretty overwhelming to cover the smell of sweat. I've had co-workers wear perfume that was so strong that it gave me headaches and I had to take it up with their supervisors. Fortunately there was compromise. We had that person cut back by half, my headaches went down and she could still use her perfume.