With your other half. It's actually really fun.
The Husband and I do it two different ways.
Get a cheap hotel room. Meet for lunch, and have a quickie. You don't need to get a seedy motel room with rats scurrying in the walls, but just a moderately priced room. It'll feel kind of naughty, and you'll walk back into work feeling a little bit awesome.
Or you can go the high class hooker route. Get a room in a hotel that can boast a few stars, put on a nice cocktail dress, and get picked up by your man. Do it on a weekday, and go your separate ways the next morning.
Seriously, the role playing opportunities are ripe, but if you're not into that, it's still something different and exciting.
We don't do this often, but when we do, it's FUN.
A word of advice though, use one of those travel sites where you can bid on a mystery hotel. You'll have to plan it a couple days in advance, but it's worth it. We got a $240 room for $89.