Forget spilling the tea. Today, we’re spilling the beans about a common coffee conundrum—why it tastes so bad when you reheat coffee in a microwave. Unlike some foods and drinks that typically taste better after being zapped (like last night’s leftovers, a cold piece of pizza, or even a cup of mineral-rich bone broth), nuking your morning cup of joe tends to have the opposite effect, giving it a funny aftertaste that makes it downright undrinkable. Hardly the best part of waking up.

The reason for this, according to London-based food scientist Natalie Alibrandi, is simple. “Coffee naturally has volatile compounds, chlorogenic and quinic acid to name a few,” she says. “When you reheat your coffee in a microwave, you’re releasing more of these compounds that can taste astringent and bitter.”

And while this happens with all coffee—no matter how you brewed it—Alibrandi says there is one technique in particular that tends to make coffee tastes even worse when it’s reheated in a microwave. “If you make your coffee using a French press,” she says, “there will be more volatiles floating around that will continue to brew and become even more bitter.”

Okay, a bit of a buzzkill. But in an effort not to end on a sour note, we asked Alibrandi for her best practices when it comes to warming coffee back up so it tastes just as good the second time around.

How to reheat coffee without a microwave

Who hasn’t found themselves sitting down to their computer with a piping hot cup of coffee only to wind up getting lost in their inbox for so long that it’s lukewarm by the time you look up? Been there, done that. When this happens, “pouring your cup of coffee into a saucepan and reheating it slowly on the stovetop could be an option for less bitterness,” Alibrandi says. “But better yet, just brew a new batch.” 

Depending on your workplace situation, these may not be feasible solutions, which is why Alibrandi recommends preventing your coffee from getting cold in the first place. “The best way to keep your coffee warm is to keep it in an insulated cup,” she says. “It will remain hot for about 30–45 minutes before it slowly starts to cool.” You can extend this window of time by investing in a mug warmer, and if none of those options are available, perhaps consider turning it into an iced coffee instead.

Our favorite thermal mugs that'll keep your coffee hot for hours

Hydroflask 20 oz. insulated tumbler — $28.00

Hydroflask really is that good. Like the brand’s beloved water bottles, each tumbler features the brand’s signature double walled vacuum insulation that keeps cold drinks hot or cold for hours on end. The sleek design is easy to carry or store in cup-holders, while the press-in lid makes sipping (and not spilling) seamless.

Yeti Rambler 30 oz. Travel Mug with Stronghold Lid — $40.00

Struggling to find the perfect tumbler that fits and your car and actually doesn’t spill? Meet the Yeti Rambler, your new go-to road trip companion. The vessel of this cup is tapered, so it fits seamlessly into cup holders while the elevated handle allows for easy access. But then there’s the lid—it screws in and seals air-tight for worry-free travel. Take it over bumps, curbs, off-roading—the thing won’t spill. It’s worth every penny.

S'well Pyrite Tumbler with Straw — $30.00

S’well was one of the first to change the insulated bottle game, and their line of tumblers, cups, mugs and more are just as impressive. Like all the others on this list, this 24 oz. cup is vacuum insulated with food-grade stainless steel that will keep your coffee piping hot and is easy to clean. But the star is the flexible stainless steel straw that makes for simple sipping in a pinch (and cuts down on single-use plastic waste while you’re at it.) In true S’well fashion, the cup comes in a rainbow of colors, patterns, and finishes. There’s literally something for everybody.

Orca Insulated Coffee Mug — $25.00

You can spend a lot of money on a fancy schmany insulated coffee mug. Or you can buy this affordable option from Orca that’s just as good, if not, even better. The 20 oz. stainless steel mug features a copper clad interior that holds plenty of coffee and keeps it piping hot throughout the day. When you’re done, toss it in the dishwasher for easy clean-up until the next time you fill up.

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