wash them and use as a candle holder

Can the returnable glass Coke bottles be recycled with regular class jars?

Glass is the best thing for rooting your cut plant slips: plastic just is too light and tips over. Glass is also good for holding craft items while you clean or heat them. It's easy to put a glass jar in a boiling water bath to heat something, plastic might melt.

I use for storing some bathroom items like cotton balls or Q-tips

When in doubt, throw it out.
Its better to do that then contaminate the recycle stream.