Five or six beers in an evening is toxic to the liver. While the alcohol is circulating, it is toxic to the brain and the rest of the body as well. If you take poison in quantities too small to kill you, you are likely to feel sick afterward.
You may have been so used to the congested or "hungover" feeling before you started cleansing that you didn't notice it. Now, you have tuned into your body's healthy song and are more affected by your body's wails of misery.
If you plan to drink, think about how to minimize the impact before you start drinking -- and execute that plan as you drink. Take extra vitamin B before you drink. Perhaps milk thistle as well to protect your liver. Feed yourself at least 12 oz of pure water for every beer you ingest.
Don't mix Tylenol (or acetaminophen in cold medicine) with alcohol -- that combination multiplies effects on the liver.
From Mercola.com "The government estimates about 100 people die each year after unintentionally taking too much acetaminophen (an overdose of the drug, which includes Tylenol, can poison the liver)."
The best thing would be to celebrate with foods and drinks that your body likes and will thank you for consuming the next morning.