When you cast a break-up spell, either or both of the partners may start arguing about so little topics. However, they are cast generally and not on a special person.
But if you aim at one single person, you can try something else beside the vinegar jar spell. Voodoo dolls are my favorite helpers when I aim at one person.
You can make a doll of that person, add some personal objects (such as their hair, nails, pieces of dress, pic, etc) then, you can charge the doll up with your energy and in other words, "make it spiritually alive" so that it can direct the energy into that person.
You can do many things with the doll. Mess with its head with a needle or burn its head. Even talking to it can have some effects. When you're done, you can either burn the doll or bury it. If you wish though, you can put it somewhere safe.
For the vinegar jar itself, burn black candles around it, meditate and charge it up, make new jars and put personal things into the mix.