Look, having Boost once in a while is totally fine, it's just milk masala after all. But don't make it a daily habit because it has empty calories and sugar. Just balance it out with a healthy diet and you are good to go.
My MIL was totally against these store-bought health drinks, she wanted me to drink badam milk only! But I used to crave Boost sometimes and had a spoon of it. If your gynac says it's okay, thoda chalega, but ghar ka doodh with kesar or badam is what my family preferred.
Honestly, I used to love Boost and had it occasionally during my second trimester, but in very small quantities. I didn't face any issues, but everyone's body is different. What worked for me might not be okay for u, so just sharing what I did.
I actually avoided all health drinks because I was too scared of the preservatives and sugar. Boost has cocoa and caffeine too, right? Best to ask your doctor once because even small things made me super anxious during my time!
Please be very careful with drinks like Boost because they have a lot of added sugar. I had gestational diabetes and my doctor strictly told me to avoid such packaged drinks. If u really want to drink it, check with your doctor first or just have plain milk with dry fruits.