Is it permissible for two sports teams to collect subscriptions from their members to cover the costs of a match and a reward for the winning team, knowing that the subscriptions are not limited to the reward only, and no third party has been found for the reward?

The reward for the winning team, if it comes from members' subscriptions, is gambling (qimar) which is forbidden by Islamic law (haram). This is because each team is suspended between gaining and losing, and this is precisely what gambling is. Allah (the Most High) said: "O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone altars [to other than Allah], and divining arrows are but defilement from the work of Satan, so avoid it that you may be successful." (Surat Al-Ma'idah, 5:90). The فقهاء (jurists) have agreed upon the prohibition of gambling (maisir al-qimar). If the subscriptions are used solely for expenses without prizes, then that is permissible.