I wouldn’t tell you it’s the best option, but it works for me and sizeable amount of other people: stateless password manager. It is an app that will generate you password based on input: url and a single master password.

Using same parameters gives the same password. Passwords are not stored, you just generate one whenever you need it. It solves syncing issues and eliminates option of losing your vault/backups. Master password should be extra secure, because it is the main defense point.

For the implementation, you could make one yourself with scripts (scrypt + base64) or use open-source apps like LessPass.