If you're drinking before hand, don't get hammered, because it can diminish the experience and (more importantly) put you at greater risk for dehydration. Pretty much the same reasons to not drink with regular MDxx, except that the APB's can get mongy and confused at higher doses more than I've ever had happen from MDxx. Personally I try and stick to only beer or wine if I'm taking any MDxx-type drugs, and generally lose interest once I've gotten high. If I drank too much, I end up coming down and getting a massive headache and low blood sugar, etc. Feels pretty shitty
As for the dosage, 125mg is on the high side for most people unless you have a tolerance to amphetamines or MDxx. If it's been a few months since you last rolled, 100mg will get most people
very high. I've shared 5-MAPB with several friends of mine who've all had experience with MDMA, and they all got "really fucking high" from 100mg
EDIT: One more thing about drinking on 5-MAPB... I really like having a beer, maybe even 2, once I've all but come down. Feels like a "night cap" and generally helps relax any lingering muscle tension and get my mind set on bed time. Having sex is even better for this, once you're able to orgasm again!