I could care less about American Hefeweizen. Make a seperate article, this is about Hefe in general. I'd like to add Granville Island Breweries to the list, but lo and behold, it's a list of American brands, and GIB is Canadian. Go figure.
The standard dosage for oral Benadryl is 1 mg per pound of body weight, given 2-3 times a day. Most drug store diphenhydramine tablets are 25 mg, which is the size used for a 25 pound dog. Always double check the dosage before giving an over the counter medication. In addition, many formulations are combined with other medications such as Tylenol so make sure Benadryl tablets contain only diphenhydramine.
Benadryl tablets are safe for dogs and generally result in a moderate reduction of stress/anxiety. You can give 1mg per pound that your dog(s) weigh. So for example, if your yorkie weighed 12 pounds, you can give them 1/2 of one 25mg tablet. I would suggest trying it in advance just to ensure that it is effective for your pets. Safe travels!