All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Putting a tablet or a sweet under the tongue during the prayer may lead to two matters that may invalidate the prayer:
Firstly, it may totally prevent the movement of the tongue while reciting the Quran, and it is known that the recitation of Al-Faatihah is a pillar without which the prayer is void. If it does not totally prevent one from the recitation, it may still lead to pronouncing some letters in a manner that invalidates the correct recitation.
Secondly, placing something that dissolves under the tongue takes the ruling of eating or drinking; if the worshiper swallows it, then this invalidates the obligatory prayer as stated by the jurists. Ibn Qudaamah said:
"If one [the praying person] puts in his mouth something that dissolves, like sugar, and it dissolves and he swallows it up, then this invalidates one's prayer because it is eating (food)." [End of quote]
If that does not invalidate the recitation and the proper pronunciation of the letters and nothing reaches the stomach, and it does not involve a lot of chewing, then the prayer is not invalidated.
We do not think that the matter of raising the sugar level depends on the minutes during the prayer. You can eat something before the prayer that will raise the sugar level and have the peace of mind during the prayer.
We believe that describing the matter (the sugar level) to be dependent on (and affected during) the time you pray is an exaggeration.
Allah knows best.