about how much would $6.88 get me at mac's convenience store?

my mom is going to pick up my baby step sister, today. she will be gone about 8 hours. I am supposed to make soup for lunch, and take my other step sister (the really mean one D:<) to the mac's convenience store by my house. we have been hundreds of times, but I don't know how much $6.88 will get me. I normally have more money. and I lost my bank card before I even started dating my boyfriend, which means it has been missing over three months. I really love chocolate, but its so expensive there, and I think all the nestle chocolate bar deals are over. I could get a slurpee, but- I just don't know. we live in Canada, if it helps. I don't really know what to do.