The v brakes on one of my bikes just keeps on squeaking. I have cleaned the pads with denatured alccohol, I have lightly sanded them, I have cleaened the rims and I have made sure they are toed in.
Still they sqeak.
Any thoughts?

What pads are you using? I use Kool Stop dual-compound on my front wheel, and they are very noisy when braking hard. On the rear, I use Aztec pads, and they are very quiet, though don't brake quite as well as the Kool Stop.

Jag Wire

Have you tried swapping the pads front to rear?

I know this doesn't help, but... I'll never buy another bike with v-brakes. I'm done fighting with them. Cantilevers and dual-pivot sidepulls work better, adjust easier and aren't as prone to squeaking.

I have not swapped the brakes front and rear. Even though the pads have enough material before the wear mark maybe i will try just putting on new pads.

Funny thing about my Magura Rim brakes, after scouring thru the CD anodizing on the rims
with their abrasive green compound, pad, swapping back the black and later salmon pads,
There never was any squealing.

That's what ended up solving the problem for me.

I have a bike with V brakes and had the same problem, and tried all the same solutions you listed in the original post, most of them at least twice. They weren't totally worn out, but I bought new pads anyway (I believe they're Jagwire because that's what my favorite local shop tends to carry). I carefully installed them, but I don't believe the toe-in was any better or worse than the original pads. I haven't had any squealing at all since then, about 1,000 miles.

I installed Avid SD7 V-brakes on my Cross check, replacing Shimano BR-R550 Cantis in an effort to stop the canti's incessant squealing. Didn't help. Fitted Koolstop Salmon pads. Didn't help. Toed the pads in some, then a lot, then flat. Didn't help.

What finally stopped almost all of the noise (not quite all but close) was substituting Koolstop's Dura Type road brake holders and Salmon road pad inserts for the MTB-type holders and pads. These shorter holders and pads must be more rigid and have finally quieted the bike down.

V-brakes come with those long thin pads and holders that want to vibrate. And it's never possible to get the entire pad in play anyway; even if you manage to get it tweaked into alignment, it won't hold the adjustment.

Google for "Brake Pad Toe In" - Sheldon Brown or the Park Tools sites are good pages on this. Alternatively some Koolstop pads have a little extra ramp on one end which helps set them up with toe in.

The OP stated...