Praise be to Allah.
If the beer is free of that which causes intoxication, then there is nothing wrong with it. However if it contains any intoxicating substances, it is not permissible to drink it. The same applies to all other intoxicants, whether they are drunk or eaten - they must be avoided and it is not permissible to drink or eat any of these things, because Allah, may He be glorified and exalted, says (interpretation of the meaning):
O you who believe! Intoxicants (all kinds of alcoholic drinks), gambling, AlAnsab, and Al-Azlam (arrows for seeking luck or decision) are an abomination of Shaitans (Satan) handiwork. So avoid (strictly all) that (abomination) in order that you may be successful.
Shaytaan (Satan) wants only to excite enmity and hatred between you with intoxicants (alcoholic drinks) and gambling, and hinder you from the remembrance of Allah and from As-Salat (the prayer). So, will you not then abstain?
And the Prophet (blessings and peace of Allah be upon him) said: Every intoxicant is khamr and every intoxicant is haraam. Narrated by Imam Muslim in his Saheeh. And it was proven from the Prophet (blessings and peace of Allah be upon him) that he cursed alcohol, the one who drinks it, the one who pours it, the one who squeezes (the grapes etc), the one for whom it is squeezed, the one who carries it, the one to whom it is carried, the one who sells it, the one who buys it and the one who consumes its price. It is narrated from him (blessings and peace of Allah be upon him) in a saheeh report that he said: Every drink that intoxicates is haraam. And it was narrated from him in a saheeh report that he forbade every intoxicant and relaxant.
What the Muslim should do is avoid all intoxicants and beware of them. The one who does any of that must give it up and hasten to repent to Allah, may He be exalted, from that, as Allah, may He be exalted, says (interpretation of the meaning):
And all of you beg Allah to forgive you all, O believers, that you may be successful
O you who believe! Turn to Allah with sincere repentance!
Majmoo Fataawa Ibn Baaz