If your goal is to build relations or ascertain information about your counterpart, drinking may be helpful. Of course, it is necessary in such cases to have high level of tolerance.
Alcohol may also be beneficial if you are the stronger side in the negotiations and you believe that showing a somewhat more irrational version of yourself could be of benefit. The key fact to keep in mind is that alcohol never improves your own performance; rather, it reduces the performance of your counterpart. So it may be more useful to drink while negotiating a zero-sum issue, where you cannot create value by negotiating constructively.
Be that as it may, it remains the case, according to an article on the INSEAD website, that alcohol invokes aggressive tactics and makes negotiators prone to mistakes.
Undesirable effects of alcohol
If you need to discuss technical issues, you will need to maintain a clear mind. Only then will you be able better to counter potential objections and choose a more prudent course of action. Refrain from drinking also when you need to make a good impression or when the risk that the conflict may be escalated is high.
You can always excuse your abstinence with some legitimate reasons:
You don’t drink alcohol.
Your doctor has ordered you not to drink.
You are on antibiotics or have stomach issues.
When declining a shot, show that you are grateful for the offer but can have only a sip. Or simply state outright that you are not allowed to touch alcohol. In most countries, an apology with a reasonable explanation will be accepted.