Things which invalidate the Fast
  1. Eating and drinking.
  2. Ascribing false things to Allah, Prophet (S) or with the successors of the Holy Prophet (P.B.U.H.).
  3. Making dust reach one's throat.
  4. Immersing one's head completely in water.
  5. *Not fulfilling Ghusls that are Wajib upon you before Azan of Fajr prayers.
  6. Vomiting.
  7. Sexual relations.
  8. Doing any such thing by which semen comes out.

*  To intentionally remain in a state of impurity caused by Janabat, Haidh or Nifas up to Subhe Sadiq of a month of Ramadhan fast or its Qaza.

Things to avoid when Fasting

  1. Eyedrops or Surma, etc whose taste or smell can be felt in the throat.
  2. Actions which would make you physically weak.
  3. Keeping a wet cloth on the body for the sake of cooling.
  4. Snuff and fragrance from sweet plants and flowers.
  5. Tooth extraction or any other action which will cause you to bleed.
  6. A wet tooth brush for brushing.
  7. Putting water or using any kind of mouthwash unnecessarily.

The above 7 things do not break your fast if you do them but it is better if you do not do them.