How to keep the fuzz in the pop always

  Ever had the experienced that you order a pizza and don't order the drinks thinking you have a 2 L soda that you bought from the market. As usual when the pizza arrived u open the bottle the pop goes flat.
  Is there an agent or a chemical that's safe that you can add to instantly give you the fuzz you need for drink...? That would save the day. Let me know if someone can come up with somthing...