These are things that invalidate wuḍū` and spoil it:

1. When something comes out from either of the two exits:

i.e. from the place that urine comes out from or the place that faeces comes out from, be it urine, faeces, pre-ejaculate, menstrual blood or wind, regardless of the quantity. The evidence for this is that Allāh -Exalted is He- says (the meaning of which translates to) “or one of you comes from the place of relieving himself” [Sūrat Al Māidah, Āyah No. 6]. And that the Prophet (May Allāh praise him and Peace be upon him] said, “Except faeces, urine or sleep.” [Graded as ḥasan (good) by Sheikh Al Albānī in Al Al-Irwā 1/141]

2. When impurities come out of anywhere else in the body:

If it is urine or faeces, it always invalidates wuḍū. If it is blood or vomit and it is unpleasant and there is a lot of it, it is better to perform wuḍū to be on the safe side. If is a small amount, there is scholarly consensus that there is no need to perform wuḍū` [Al Fiqh Al Muyassar (Islamic Jurisprudence Made Easy): 32].

3. Losing one’s senses, losing consciousness or sleeping:

The evidence for this is that the Prophet (May Allāh praise him and Peace be upon him) said, “Except faeces, urine or sleep” and “The eye (when awake) is what prevents one from passing wind. So, if somebody sleeps, he is to perform wuḍū.” [Graded as ḥasan (good) by Sheikh Al Albānī in Al Al-Irwā 1/148]. There is scholarly consensus that insanity, loss of consciousness and intoxication invalidate a person’s wuḍū`.

4. Touching one’s genitals with no barrier:

The evidence for this is the ḥadīth (narration) of Busrah Bint Ṣafwān (may Allāh be pleased with her) in which the Prophet (May Allāh praise him and Peace be upon him) said, “Whoever touches his genitals is to perform wuḍū.” [Authenticated by Sheikh Al Albānī in Al Al-Irwā 1/150].

5. Eating camel meat:

The evidence for this is the ḥadīth (narration) of Jābir Bin Sumrah in which a man asked the Prophet (May Allāh praise him and Peace be upon him) “Should we perform wuḍū after eating the meat of sheep and goat?” to which he replied, “If you wish, perform wuḍū, and if you do not wish to, do not.” The man said, “Should we perform wuḍū after eating camel meat?” to which he replied, “Yes, perform wuḍū after eating camel meat.” [Reported by Imam Bukhārī: 360].

6. Apostating from Islam:

The evidence for this is that Allāh -Exalted is He- said (the meaning of which translates to) “And whoever denies the faith - his work has become worthless” [[Sūrat Al Mā’idah, Āyah no. 6].

7. Everything that makes ghusl (bathing) obligatory makes wuḍū` obligatory

[Al Fiqh Al Muyassar (Islamic Jurisprudence Made Easy): 33]