Then you can wait during the day.... 3 to 4 hours after eating...and try it before the next meal. (no snacks before). And wait about an hour. Take with a little water--like 4 ounces or so.

Food present in the intestine, will block absorption. You can take it during the day, but just time it so there is less food around likely. Fiber in the food is the worst factor. But volume is also a big factor. Food binds and holds the B12 away from the lining of the intestine and prevents passive absorption.

Sublingual use is really not efficient. I wouldn't count on it. People with intact intrinsic factor in the stomach do better, with absorption too. But that is very difficult to predict.
The B12 molecule is huge and water soluble, which are 2 chemical factors going against mouth absorption. Also the mouth is a very small area and many drugs just don't pass thru the membranes of the mouth easily. It can take a LONG time and daily use then tends to cause mouth irritation. Most of the B12 is dissolved in the saliva and is swallowed.