You can get plasma packs, this weird fruit or you can feats on Sims! What is cool about drinking the blood of Sims is that you can actually ask their permission first and if you are friendly enough with them, they may let you have a little snack on their blood! That is cool if you want to be a friendly vampire, but if you want, you can just take it by force and drain them as much as you want. There are a few different ways you can get blood.
