I have bottle cages similar to these ones and I don't like that my bottles get scratched after a while. Will this also happen with plastic or carbon fiber cages? I don't like the idea of having to buy new bottles every time they look all scratched. Any tips will be appreciated.
I think that's a generic chinese bottle holder cage with the word "Bontrager" printed on it. The price alone implies its not "authentic".
Any cage that employs friction as a retaining mechanism will scratch up bottles/bidons after a while.
limit the scratching, using a layer around the bottle (a clean sock soaked in water used to be a pro thing to keep the bottle cooler)
buy a bottle like this - it clips onto two bosses. keyword: "cageless"
- buy a bottle like this - it uses magnets in the mount to attract the steel ring on the bottle. Keyword "koala bottle"
Hydration backpack. Had to put it in as an option, and the roadies are all thinking "hellno!"
Buy an adapter like this - removes the need to slide bottle in/out while riding. Downsides, looks a bit weird, and you still have to take the bottle out to fill and wash. Keyword "h2bike"
Apply rule #5. My bottles last about 3 years on average before cracking or the thread goes wonky, or they vanish down a hillside after a crash. I get a couple bottles a year from events that I go in, so there's always some around. Last resort is to use 500-750 mL drink bottles, like flavoured milk or various carbonated beverages. They may not have a sippy lid but work well enough as the second bottle.
You don't have to buy new bottles every time they look scratched -- they're still perfectly functional as water bottles.
Depending on cage design, you may find that plastic or carbon fiber cages don't scratch bottles as much (but you have essentially some light paint on a water bottle, and if you rub it enough with any bottle cage it will eventually come off). An adjustable cage (like the Topeak Modula EX) may help as well, since you can have the cage adjusted to the point where it just grips the bottle.
If you really care about the aesthetic, you can attach some felt or other non-scratching substance to the parts of the bottle cage where the bottle comes into contact with the cage. This can be done with tape or glue. Alternatively, you can buy a different type of bottle with less scratch-able decals.