Friendly reminder: vitamin D3 can affect sleep if taken later in a day. I tend to skip if I forget to take it before noon. Also, D3 without additional K2 may lead to calcium excess.
While there are studies on 25-OH-D metabolism impacting melatonin production, I can only find studies done with Multiple Sclerosis patients [1]. There are also studies showing that LOW levels of 25-OH-D may have negative impact on sleep [2][3][4]. While I am unable to present scentific evidence, I would like to state that for me - personally - taking vitamin D3 in the afternoon has similar effects to ingesting caffeine. I have no reason to believe that I might be suffering from Multiple Sclerosis. Without evidence you are free to ignore it as a placebo/nocebo effect. YMMV based on age, ethnicity, sunlight etc.
The "take with meal" instruction is common with substances requiring fat for absorption/bioavailability. Dietary fat increases vitamin D3 absorption [5].
[3] https://pubmed.ncbi.nlm.nih.gov/28652922/ The relationship between serum vitamin D levels and sleep quality in fixed day indoor field workers in the electronics manufacturing industry in Korea
One more friendly reminder: If Vitamin D dosage is above 4000IU, same amount of Vitamin A should also be supplemented to avoid Vitamin A deficiency (e.g. eat liver). It's also antiviral, so it sounds like a good idea anyway.