It might be a dumb question but I don’t want to risk fucking him up somehow—what I’m most worried about is his stuffing getting mildew-y or otherwise borked. I’m pretty sure, almost certain actually, he’s polyester inside. Do I just dunk him in some soapy water, scrub him, and leave him in the sun for a while? Can I throw him in the washer next time I do laundry? He’d fucking love that.
Warm soapy water, hand wash, thorough drying in the air but out of direct sun.
Probably you could throw him in a laundry machine, but maybe use one of those laundry bags that are used to protect delicates like bras.
Use a cold wash, like 30C or whatever that is F, the coldest setting the machine has that isn’t literally just cold. Detergent requires some heat to activate but typically 30C is sufficient and you want to be at that minimum to be safe.
Hand washing in water that is warm like a gentle bath is likely best.
Then the key thing is really letting him dry. Thorough drying. Don’t put him in direct sunlight.
Do NOT use fabric softener.
Do NOT wring him dry. Just let him air dry.
What the other comment said is good, just want to add:
Use a lower spin speed if you're going to use a washing machine and use a tight-fitting delicates bag or tie a knot in a delicates bag if it's too big - not tight enough that it's going to squeeze any air out of your toy but tight enough like you're packing it into a bag. This will help ensure that the stuffing doesn't get shifted around too much.
If it's small you might use a sock instead of a delicates bag. You could also use stockings, an old t-shirt, or a pillowcase.
The other thing I'd recommend doing, especially if it's larger, is after the wash placing it between a dry towel or something similar and giving it a reasonable press on all parts of it to get the excess moisture out before air drying. Don't wring it but a firm press on a flatter surface between a towel or two will get a lot of moisture out and it will ensure that the toy dries properly without getting mildew-y
