How do you wash your baseball caps?

Just hand-wash it in a basin with water (temp depends on the fabric, but probably lukewarm is fine) and a mild soap. Tumble it around to work the suds through, let sit for an hour or so, then rinse well and let air dry. For what it's worth I've even just thrown hats I don't care about ruining in the washer and had no issues with deformation But I wouldn't recommend that if you really like the hat and fear damaging it.

If it isn't so dirty, just pre-treat the headband area... You could hand wash or soak it if you're worried about it, but I usually run them through the wash, no machine dry, and they turn out fine. I don't fuss with blocking them or stuffing them with paper, as some I know do.

Years ago I saw a plastic device one stretched the cap over, and it could go into a dishwasher... Seems a bit nasty.... but I think many Americans would probably buy it.

So, it's okay for the bill to get wet? I thought it would I don't know get less solid or something, droop.

Thanks!

Maybe if the bill/visor's base is cardboard, it might get a bit wonky. But I'm pretty sure if you let it thoroughly dry before wearing, it should be fine. Most cap visors are fabric covered plastic, not cardboard. At any rate, either should be able to withstand a light washing.

Pretty sure you can dry clean them. I just spot clean and use one of those do-it-yourself dry clean products that you throw in your dryer.

I wear hat, all I do is wash them in cold water in a huge bowl in the kitchen sink. And let it sit and dry. I turns out fine, but seems to fade over time unfortunately.

My hates are mostly black.

As a youngin’ I used to wash them in the dishwasher with some sort of baseball cap washing contraption. Did a great job.

Mary!

OP, you didn't tell us what kind of fabric the cap is made of. You didn't tell us what stiffening material was used in the bill. I appreciate that you might not have those answers, but if you don't have them, certainly none of us do.

I accept that your ex is a lunatic, because only a lunatic would make his own baseball caps. But without any facts about the actual hat, no one can can give you a dependable method for cleaning it.