@Samantha ... There is a variety of juices that are known to "crack" polycarb, plastic, acrylic tanks. We call these "tank crackers"... No one really knows why. The assumption is the acidic nature. If you are unsure if one of your juices is a "tank cracker", it's best to check with the vendor.
"Tank crackers" can do more than just crack the tank... some will cause the tank to look hazy... some will "melt" the plastic insulator... some will actually cause little cracks all around the bottom. Though these juices are not considered harmfull to vape, they will/can damage your tank.
It's not an all the time occurrence... I've had everything below in plastic tanks with no problem. In almost 3 years vaping I've only had it happen maybe 10 times.
Known flavors to be tank crackers:
- banana
- cola
- root beer
- citrus (lemon, lime, orange, tangerine)
- hot cinnamons (like the fireball type, not bakery)
- pineapple