Cooling down on the bike is far more efficient than standing around.
You will have to figure out how far you need to cruise to cooldown but you should be pedalling at a really gentle pace, basically rolling along. Save a waterbottle for the cooldown and splash it over your head, shirt and shorts. You need time on cruise to evaporate and cool you.
You can get twin bottle holders that bolt to the seat rails.
Keep an extra set of clothing at work for the time you forget stuff.