There shouldn't be sugar in your methylB12. This one which was at one time the only available form in US 10 yrs ago and by online purchase, does not have sugar in it:

Jarrow Formulas : Methyl B-12

We use now a locally available generic form from Costco, which also does not have sugar. Since historically B12 was sublingual before research showed it to work orally (swallow) there at one time may
have had sugar in them. But today they use artificial sweeteners in the tablets in case people still want to use them under the tongue.
Xylitol and mannitol are examples of sugar substitutes, and you might find sucralose (Splenda) in some brands.

One thing that seems to be lacking in studies on B6 elevations, is the fact that inactive B6 (pyridoxine) has to be activated to P5P the active form in order to work in the tissues. B2 (riboflavin) is a cofactor in the enzyme called pyridoxal kinase that does this job.

There also are drugs that inhibit pyridoxal kinase binding:

The conclusion of this article lists them at the end:
http://scholarscompass.vcu.edu/cgi/v...07&context=etd

Caffeine! That would be an issue for many people I expect.
So elevated B6 in serum could point to inefficient conversion of pyridoxine to P5P. This is one reason that P5P is more common today as a supplement. In fact one RX company was planning a drug containing only P5P in it. And there is another called Metanx that has P5P with methylcobalamin and methylfolate in it which is also RX in the US.