My husband has vascular dementia. How do I deal with incontinence? He wets himself every time he urinates. I’m constantly washing clothes.

What to do depends quite a lot on what exactly is going wrong. Is he not managing to get there on time? Is he not pulling his clothing out of the way, but not realising? If possible, if you're not already doing this, try to catch up with him when he heads to the bathroom so that you can observe what happens, and either prompt him verbally or intervene.

If the laundry is getting you down (and who could blame you - the sheer quantity of it often doesn't dawn on people until they've been there themselves) and you live in a town, see if there's a collection and delivery service you could use. It's well worth the money.

Having him sit on the toilet would be the best option and actually a safer one if he is at risk for a fall.
At night using a urinal might be an option
If he would not fuss with it a condom catheter might also be an option.
It depends on how severe the dementia is if you can get a man to change from a standing to sitting position to urinate.
I am going to assume that you are using a pull up or tab type incontinence brief. If not and he is not making it to the bathroom, or forgetting to go to the bathroom and he is wearing regular underwear you need to switch out all his underwear with pull up briefs.

I have been there done that with my husband who also had vascular dementia. On top of wearing Depends, my husband tried all the different medications out there to help with incontinence, his urologist put Botox into his bladder to try and help, and none of that helped. At night my husband was getting up every hour on the hour to pee, and because he was a fall risk, I had to get up with him. Often I would just hold the plastic urinal for him(he only had use of one arm due to stroke)so he wouldn't have to get out of bed. But often still he would be wet along with the waterproof pads, and so I was doing laundry daily. It got to the point where I had to insist that my husband sit down on the toilet seat when he had to pee, because like your husband he always got pee on his clothes too. My husband didn't like it at first, but eventually got used to it.
After us both reaching the point of pure exhaustion, his urologist finally recommended that my husband get a supra pubic(permanent)catheter, which he did get and what a Godsend that was, as we were finally after almost a year, finally able to sleep through the night. I only had to empty the catheter bag twice a day. You can always ask about a condom catheter or some other type if you don't want him to get a permanent one. Your husbands urologist can help you with that.
It's hard to deal with, I know, but hopefully you can get some much needed help from your husbands urologist. I wish you the best.