1581. * There are nine acts which invalidate fast:
(i) Eating and drinking
(ii) Sexual intercourse
(iii) Masturbation (Istimna) which means self abuse, resulting in ejaculation
(iv) Ascribing false things to Almighty Allah, or his Prophet or to the
successors of the Holy Prophet
(v) Swallowing thick dust
(vi) Immersing one's complete head in water
(vii) Remaining in Janabat or Haidh or Nifas till the Adhan for Fajr prayers
(viii) Enema with liquids
(ix) Vomiting
N:B Please Refer to Resalah For more details.
source : www.tebyan.net