No, there's no stupid "steam the veggies in the shower" trick here. (But man, can we make that into a meme?)
In fact the quickest way to deal with a microwave-less hotel room is often the simplest: Simply ask the hotel if it's possible for them to bring a microwave up into the room. It's a weird request, but if they're able, most hotels will happily oblige.
Other than that, there are plenty of extreme hotel cooking techniques and gadgets—especially the travel-friendly HotLogic Mini Personal Portable Oven that can cook frozen, raw meats—that work well in lieu of a microwave.
Microwaves may not be a standard amenity, but they should definitely be one, and with hotels like the Holiday Inn upping their game (it's hard to know what you're missing when everything is there), it's tough not to be critical in this day and age.
So upon our arrival to find one of these rooms at the Kimpton Marlowe, the situation was quickly fixed with a call to the front desk. Ladies and gents, presenting to you, the microwave!
Thanks for the beautiful, warm apple cider donuts (and chilled wine).