25-30g Whey protein (I also add 5g creatine monohydrate). And why....
Research shows that while whey protein causes an increase in serum levels of leucine, isoleucine, and valine, it also causes an increase in the hormone glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). The most interesting finding in this study is that not only did whey protein caused an increase in serum insulin levels, it caused an increase of insulin, GIP. GLP-1 greater than carbohydrates from white bread (1).
This study found that after ingestion of whey (grey bars), white bread (the carb group, white bars), and glucose alone (reference, black bar), whey protein caused the biggest spike in insulin (figure 1).
These findings of this study was backed by further research, thus confirming that simply supplementing 100% whey protein causes significant insulin spikes (2).
https://pescience.com/blogs/blog/lesson-9-avoid-massive-insulin-spikes-from-your-whey
Personally i dont add carbs to intra workouts. Dont see the point as my body has more than enough stored eating 300g a day. Whey protein provides the building blocks of lean muscle, gives me that insulin spike to transport it all to the muscles and give that nice atp release from the creatine being transported there as well. i dont pay for the gimmicki intra workout BS. Cheap whey isolate and creatine monohydrate. Best stack ever.
https://www.ncbi.nlm.nih.gov/pubmed/18430966