Glucose/Dextrose is by far the fastest because the molecule does not have to go through any changes to be used by the cells, unlike fructose. Lots of water gets it past the stomach, even with gastroporesis, so it gets to the intestine where it can enter the blood stream faster.
I've found the cheapest way is to buy powdered dextrose and mix it with water and keep it in a sports water bottle. Powdered glucose is available through some baking outlets or sports supplement stores. I buy a 10 lb. tub for $18.76 online and it'll last me for a year or more, Dex4 (4gmC) tabs cost close to $5/100tabs. Powdered has 10C/tablespoon.
I've found that it seems a little faster than chewing the tablets followed by water but not much.
I've also found that when severely low I'll chew up a glucose tab and pack the paste under my tongue and gums. where the glucose can enter the blood directly.