Spend the money and get concert earplugs. Not only will it save money (a basic set is only about $30), and fit better, but the event will sound better. Those foam ones are great to protect your ears, but they muffle the sound. Great if you're around power tools and the like, but terrible if you're at a concert

Concert earplugs (I have Loops, but there are countless options and each has its fans) lower the volume without significantly changing the sound. You can still hear your favorite songs, and they sound correct.

If you are using disposable earplugs, then throw them away. I used to wash and reuse them, and got some nasty ear infections as a result. It's just not worth it. It would be batter to buy a pair of loop earplugs.

Get reusable ones

You don't, these are single-use for a reason.

I got some Etymotic reusable plugs and I never leave home without 'em. They come with a little carrying case, and they don't affect the frequency response of my hearing (just the overall decibel level!)

You can get construction ones for something like 25 pairs for $5. Just throw them out once they get dirty.

I would just buy a pair of Loops, come with a little carrying case as well.

You can get this: 100 pairs for like $25

https://a.co/d/3Bt0170

You really should throw them away. They are porous so cleaning is not going to work well. They are meant to be disposable.

Or get longer-term ones if you want better quality sound for music. I have a pair from EarPiece that I use. They have much better sound distribution, adjustable components to change the protection level, and they can be cleaned with alcohol. Plus they come with a nice case and an extra plug in a separate compartment in case you lose one while at an event.

Given you use them often, I would go for professional earplugs. Anything above €25~30 would be infinitely more comfortable than disposable ones, and you would still be able to understand people talking to you. If you feel extra fancy and have the cash (€150+) there're some you can adjust the level of attenuation so you could use them at a concert as well as, let say, the super market.

As others have said, they're usually disposable. If not, or if you want to try cleaning them anyway, try putting them into a mesh bag or something similar, then put them in the washing machine on a gentle wash cycle and let them dry naturally.

Obviously, try this with a small amount first, so that if they don't survive the process it's not the end of the world. If you don't have a mesh bag, a clean sock should be ok, just tie the end closed.

You can wash them in the sink with warm water and a little bit of soap too, but it's more work. Just remember to rinse them thoroughly before they go back in your ears :)

If you must I use a little bit of bio-degradable all-purpose cleaner from ZEP, and then wipe it down again with a damp cloth; however, I've also found that the older single-use ear plugs don't work as well, so do try to get a proper pair of re-usable ones.