1. Generally speaking, anything that has a considerable harm for the body is haram to consume.
Considering the substantial individual and societal harms of drugs, they are haram.
Therefore, you shouldn’t be using such things, although they do not invalidate the fast when taken the night before.
2. If you want to wake up at dawn during the holy month of Ramadan, you shouldn’t resort to haram means, especially in such a blessed month, the month where we are the guests of Allah.
3. Therefore, you should try waking up by sleeping early and having a light meal before bed. It is also good if you read the last verse of surah Kahf before sleeping, Imam Sadiq (AS) has been narrated to say: “If a person recites the last verse of surah Kahf, he will wake up at any time of the night that he desires.”
 Majma’ al-Masaa’il (of Ayatullah Golpaygani), vol. 3, p. 64.
 Tawdih al-Masaa’il (annotated by Imam Khomayni), vol. 2, p. 1017, inquiry 1402 and p. 1018, inquiry 1407.
 Kulayni, Al-Kāfī, vol. 3, p. 540, Daar al-Kutub al-Islamiyyah, Tehran, 1986 “مَا مِنْ أَحَدٍ يَقْرَأُ آخِرَ الْكَهْفِ عِنْدَ النَّوْمِ إِلَّا تَيَقَّظَ فِي السَّاعَةِ الَّتِي يُرِيدُ”.