I’m sure this won’t be a total rehash of U. I mean, these letters are nothing alike.
First, go look at the alphabet gif and you’ll see that there was no V before early Latin script evolved into modern. That’s because the symbol V was interchangeable with U—basically, some people wrote the letter round, some people wrote it pointed. But everyone pronounced it U. As for the sound V…they wrote that using F. When they wanted to use the F sound, they paired F with H, similar to how we use sh and th. Until they made their own symbol for it, a lost glyph that looks like an 8.
Okay, so we know V was U, so let’s look more at the history of the symbol. Early Latin sometimes wrote U as a Y—well, there was no Y then, so it’s not like it mattered. Etruscan did the same thing, using Y and V interchangeably for the U sound. The Greek upsilon has a lowercase that looks like a cross between a v and a u (υ), while the uppercase just looks like Y (the Y sound was under its domain, so it makes sense). Before that was the Phoenicianscript, but since they only used consonants, there was no symbol for V. When the Greeks first adapted the alphabet, they used the Phoenician waw symbol, which looked like a Y and sounded like a W, to create their V.
TL;DR: Everyone makes up their own sound for letters. It’s a miracle we can communicate at all.