This week Professor Christine Morrison at the Colorado School of Mines shared a picture on twitter in which she was using 2-liter plastic pop bottles to culture bacteria in a shaker instead of using glass 2L Erlenmeyer flasks which cost ~$100 each.
For those who are skeptical, there are a lot of papers about growing E. Coli in 2L plastic bottles and a lot of citations, for instance Cynthia Sanville Millard, Lucy Stols, Pearl Quartey, Youngchang Kim, Irina Dementieva, and Mark I. Donnelly wrote a paper in 2003 about this method that has received over 50 citations, and another paper written in 2005 by Hassan Sreenath, Craig Bingman, Blake Buchan, Kory Seder,Brendan Burns, Holalkere Geetha, Won Bae Jeon, Frank Vojtik, David Aceti, Ronnie Frederick, George Phillips Jr. and Brian Fox has over 100 citations.
2 L plastic soda bottles are already baffled at the bottom for aeration, and because they are practically free you can dispose of them after use to prevent cross-contamination between growths. For projects which still struggle with cross-contamination even after an autoclave cycle this is a huge benefit. It does however bring up the downside of using soda bottles: Polyethylene terephthalate (PET) plastic which makes up soda bottles cannot be put in a autoclave. Instead sterilization relies on bleach, antibiotics, and a single-use protocol.