Can someone reuse their sister's bloody tampon to save money?

No, you can't reuse someone elses tampons.

You can however use reusable menstrual products:

  • Menstrual cups.
  • Reusable softcups.
  • Menstrual sponges.
  • Cloth tampons.
  • Cloth pads.

Reusable menstrual products are actually more hygienic than disposable options, for example menstrual cups or softcups don't harbor bacteria like tampons and keep flow away from the vagina so don't change pH, sponges and cloth tampons aren't as favourable to bacterial plus don't contain any nasty chemicals, and cloth pads are just as breathable as underwear so keep you drier.

Reusable menstrual products are more hygienic as well as healthier so less risk of bad odour, irritation, discomfort, allergic reaction, vaginal infections, toxic shock syndrome, also you can see both reduced flow and reduced cramps with reusable options too.

Reusable menstrual products obviously safe money, menstrual cups being the cheapest menstrual product on the market - menstrual cups on average cost around $35 (although shopping around you can find much cheaper brands and deals) and will last for up to 10 years.

No, that's extremely unsanitary. Tampons are one area where you should spend money, it's worth it.