Based on the available information, the specific cause of the "punch sticking issue" with amino acid tablets, including those found in energy drinks like Advocare Spark [2], is not directly addressed. However, I can provide some context that may be helpful in understanding this issue.

Firstly, it's important to note that amino acids are the building blocks of proteins, and they play a crucial role in many bodily functions, including muscle growth and repair [1]. When amino acids are compressed into tablet form, they can sometimes stick together, causing what is referred to as the "punch sticking issue."

There are several possible factors that could contribute to this issue. One potential cause could be the presence of moisture or humidity, which can cause the amino acids to clump together [3]. Another possible factor could be the manufacturing process itself. If the tablets are not compressed with the correct amount of force or if they are not allowed to dry properly before being packaged, this could also lead to the "punch sticking issue."

It's also worth noting that the texture and solubility of amino acids can vary depending on the specific type of amino acid and the manufacturing process used [1]. Some amino acids may be more prone to sticking than others, and certain manufacturing processes may be more effective at preventing this issue.

In summary, while the specific cause of the "punch sticking issue" with amino acid tablets is not directly addressed in the provided sources, possible factors could include moisture or humidity, the manufacturing process, and the texture and solubility of the amino acids themselves.

Sources:
[1] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC29337668/>
[2] <https://www.amazon.com/Advocare-Spark-Energy-Fruit-Punch/dp/B06XGL55ND>
[3] <https://www.drugpatentwatch.com/p/tradename/AMINO>